Use of monoclonal antibodies in human transplantation Jacques Dantal and Jean-Paul Soulillou Clinic of Immunology

and Research Unit INSERM,

Nantes, France

Monoclonal antibodies are of growing importance in human organ transplantation in the prophylatic and curative treatment of cellular rejection. Among the pan T-lymphocyte monoclonal antibodies, 0KT3 has been much studied, although clinical research is engaged with more selective targets of allorecognition and/or their consequences, for example monoclonal antibodies directed against the interleukin-2 receptor, adhesion molecules and CD4 molecules. We summarize the use of these monoclonal antibodies and bioreagents in clinical transplantation. Current Opinion in Immunology

1991, 3:74&747

the new therapeutic tools and molecular biology techniques such as humanized mAb or fusion molecules.

Introduction Bioreagents used in allograit transplantation were first rest&ted to anti-lymphocyte polyclonal y-globulins (AI&), but now comprise a growing family of monoclonal antibodies (mAbs). The therapeutic potential of polyclonal antibodies targeted against human lymphocytes was shown by Monaco in 1967 [ 11. Since then, various kinds of polyclonal sera, including those directed at thymocytes, thoracic duct lymphocytes, T-cell immortalized cell lines and normal alloreactive T-cell clones, have been used. AGIS have been commonly used for the past 2 decades and remain among the most powerful immunosuppressive agents able to prevent or to reverse rejection [2]. Nevertheless, AL& are associated with side effects (fever, serum sickness etc.) and with a high incidence of severe opportunistic infections and lymphomas when used with other immunosuppressive drugs. This was particularly so at the beginning of the cyclosporin A (CsA) era [3]. A better understanding of the surface membrane molecules implicated in the immune response and of the ability to produce mAbs against a wide range of surface dete rminants has enabled the design of new speciiic and ‘intelligent’ means of targeted immunosuppression. To date, besides rabbit or horse ALG or antithymocyte globulin (ATG), only 0KT3 [4], a mouse mAb directed against the a-determinant of the CD3 complex, has been used on a large scale in the treatment of human allograft recipients. However, many other mAbs directed at several molecules involved in immune recognition are under study in pilot or randomized trials. In this review, we will focus on the mobs that have been used in the treatment of allograft recipients in the clinic. We will also discuss the new possibilities offered by some of the mobs that are still being studied in experimental models, as well as

Reagents that interact with all T lymphocytes Anti-CD3

0KT3 is a mouse mAb (IgG2a) directed against the 20 kD glycoprotein chain (c-chain) of the CD3 complex, which ilanks the T-cell receptor (TCR) for antigen, and has been studied extensively in human allograft recipients [4]. 0KT3 was introduced into clinical practice by Cosimi et al. in 1981 [5] and has been marketed since 1986. It is now widely acknowledged that OKT3 is a powerikl immunosuppressive agent for reversal of acute rejection [6]. More recently, it has also been shown that it is able to prevent rejection in prophylactic protocols [7]. OKT3 has been shown 141 to reverse acute cellular rejection in 94% of kidney transplant patients compared with 75% reversal by high dose steriods. It has also been shown to be effective in the rescue of steroid- or ATGresistant rejection [8]. In kidney transplantation, patients responded to OKT3 within 20 days of the onset of treatment, whereas delayed responses (30-l 16 days) were reported in cases of steroid- or ATG-resistant rejection [8]. However, recurrent rejection episodes occurred in 66% (without CsA) [4] compared with 33% (with CsA) [9] of the OKT3-treated patients. In prophylactic protocols, patients treated with OKT3 experienced fewer rejection episodes than those treated with ATG (1.5f0.2 versus 2.2f0.2 episodes of rejection per patient) during the first l-3 months post-trans-

plantation and required less chronic maintenance of immunosuppression in cardiac transplantation [lo]. However, some recent randomized prospective trials on kid-

Abbreviations A&-anti-lymphocyte polyclonal y-globulin; ATC-antithymocyte globulin; AU--azathioprine; CMC-complement-mediated cytotoxicity; CsA-cyclosporin A; DTD-delayed-type hypersensitivity; ICAM-intercellular adhesion molecule; Iflrtinterferon; IL-interleukin; IL-2R-IL-2 receptor; LFA-lymphocyte function-associated antigen; rnAb--monoclonal antibody; NK-natural killer; TCR-T-cell receptor; TNF-tumor necrosis factor

@ Current Biology Ltd ISSN0952-7915

Use of monoclonal antibodies in human transplantation Dantal and Soulillou

ney transplantation showed that 0KT3 and ATG lead to similar patient and graft survival rates and to a similar incidence of rejection and serum creatinine levels [ 11 I. In these studies, OKT3 was generally used at 5 mg day- l intravenously for 10-14 days. Lower doses, however, (e.g. 22 mg over 10 days) may give excellent results in induction protocols of renal transplantation [12]. The OKT3 mAb recognizes the CD3TCR complex and targets all mature T lymphocytes including resting T cells. It is, therefore, more specihc than ATG, which also binds to monocytes, natural killer (NK) and B cells. In vitro, OKT3 inhibits the generation of functional effector T cells and the activity of mature cytotoxic effector lymphocytes [ 131.Following in viva0KT3 administration the number of peripheral blood lymphocytes drops dramatically and T lymphocytes that do reappear fail to express CD3, although the other T-cell antigens are normally expressed [I4]. The mechanism of the in vivo disappearance of CD3 from the surface of T lymphocytes is referred to as modulation and is reversible after the interruption of the treatment Consequently the T cells of patients treated with 0KT3 fail to respond to T-cell-dependent antigens, particularly those expressed on the transplanted organ. The effectiveness of OKT3 can be monitored in vivo by measuring the decrease in the number of circulating CD3+ cells, which must be maintained below lOl.tl-l for successful treatment. However, in acute kidney rejection, some reports [15,16] show that there is no complete elimination of CD3 + cells in the graft at the usual 0KT3 doses, and describe changes in the local T-lymphocyte populations with a shift toward an increase in CDs+ and 2H4+ cell populations [17]. Therefore, the monitoring of CD3 treatment that is based on the decrease of circulating CD3+ cells and, to a minor extent, on the measurement of the 0KT3 plasma levels (levels of w 900 ng ml- 1 correspond to a concentration that blocks the cytotoxic T-cell function in vitro) may not be fully predictive of the protection given to the patients [WI]. The major problem associated with the use of 0KT3 is the occurrence of severe adverse side effects in a majority of patients at the beginning of treatment. lypitally, the symptoms start 45-6Omin after the 0KT3 injection and last for several hours. They include high grade fever (%%), chills (57%) tremor (lo%), gastro-intestinal symptoms (vomiting ll%, diarrhoea 13%) pseudomeningitis and increased vascular permeability [19]. Pulmonary oedema is seen, although rarely, in patients with previous fluid overload [4,5]. Therefore, care must be taken to prepare the patients adequately prior to the first 0KT3 injection. These side effects are ‘self limited’, and are restricted to the initial two or three OKT3 in jections. It has been shown that these clinical events are related to the massive (although transient) release of cytokines, including tumour necrosis factor (TNF)-a, interferon (IFN)-y, interleukin (IL)-2, IL-3 and IL-~ [20] into the patient’s circulation [ 211 . They are not released after the second or the third 0KT3 injection by which time the CD3 marker has been modulated. There are at least three main, but not mutually exclusive, mechanisms that might explain why OKT3 induces such a massive release of cytokine: T-cell opsonization, trapping and lympholysis of

OKT3-coated cells by macrophages with a subsequent re-

lease of cytokines; the specific capacity of OKT3 to induce T-cell activation in vitroand in vivq or the released lymphokine activates macrophages, or OKT3 bridges T lymphocytes on macrophages/monocytes, resulting in natural activation [22]. There is evidence to contmdiet the first hypothesis: other anti-T-cell mAbs (antiCD2, CD4 and/or CD8 mAbs) do not provoke this phenomenon. Two therapeutic procedures have been proposed to decrease the severity of the induced symptoms. In humans, as in mice [ 231, corticosteroids are efficient at reducing side effects if given at a high dose (0.5-l g intravenous bolus) 1 h before the injection of 0KT3 [ 240.1. Corticosteroids not only act as anti-inllammatofy agents, but also decrease the amounts of cytokines released by inhibiting the transcription of specilic mRNAs or by interfering at a post-transcriptional level by repressing protein synthesis. Furthermore, in both mice and humans j25.1, anti-TNF-or mAbs have been shown to decrease 0KT3 side effects when injected in conjunction with antiCD3, confirming the major involvement of TNF-a in this syndrome. Another recently suggested side effect related to OKT3induced lymphokine release is nephrotoxicity with an average 31% increase in serum creatinine at the beginning of acute rejection treatment by 0TK3

[261.

The second limiting factor in the use of OKT3 is the development of antibodies against it in the recipient. Although no serum sickness is observed, the xenosensitization may result in the total abrogation of the mob effectiveness. In the recipients of 0KT3 antibodies of Iglvl and IgG isoiypes, both anti-isotypic and anti-idiotypic, are usually produced. However, only anti-idiotypes (of the IgG isotype) seem to be able to neutralize the OKT.3 immunosuppressive capacity [ 271. Several procedures have been proposed to decrease such anti-0KT3 immunization They include variations in the associated immunosuppressive treatment: 7O-100% immunization was reported when OKT3 was used alone [4], compared with 25% when 0KT3 was given in association with low doses of corticosteroid and azathiopnne (AZA) [28], and 15% when a quadruple therapy was administered with CsA given at 50% of its usual maintenance dose [93. In these studies, recipient anti-0KT3 immunization was proportional to the inverse of the amount of immunosuppression given during OKT3 treatment, In animal studies, the concomitant use of anti-CD4 mAb suppresses the antibody response to anti-CD3 mAb [ 291. An increased incidence of viral infection (61% cytomegalovirus and Epstein-Barr virus) during or shortly after 0KT3 treatment compared with conventional therapy using corticosteroids or AZA (39%) has been reported [30]. Data available comparing 0KT3 with ATG show either no differences or a higher proportion of infectious episodes with ATG [ 111. Prophylaxis with trimethoprim-sulfamethoxazole may therefore be especially recommended during and after treatment. Finally, it has been shown that prolonged use or the reuse of 0KT3 is associated with a dramatic increase in the incidence of lymphoproliferative disorders. This is clearly

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related to cumulated doses of 0KT3 in cardiac transplan Won as 35.7% of patients who received more than 75 mg but only 6.2% of patients who received less than 75mg developed such disorders in a recent study [31*].

formational changes of the IFA- molecule. These in vitro effects and the observation that an anti-LEA-1 mAb (anti-CDlla mAb) can abrogate allograft rejection in the mouse are the basis for clinical trials [37].

Several other mAbs directed against the CD3 complex or a monomorphic epitope of the heterodimeric c@ TCR have been tested recently ln human kidney transplantation. Although other anti-CD3 antibodies (WT32; murlne IgG2a) did not reduce cytokine release [32], mAbs against the a$ chain of the TCR (TlO B9 lA31; murine IgM mAb) hold greater promise [33*]. This mAb effectively reversed acute kidney rejection with less severe side effects than expected. This may be attributed to the non-mitogenic nature of the mAb although it still remains able to modulate the CD3-TCR complex at the T-lymphocyte surface. Another anti-as TCR mAb (BMA 031; murine IgG2b) was also studied in prophylaxis. This was not very effective at a dose of 5 mg day- 1 for 7 days (78% of patients suffered acute rejection), but much more effective when given as a ‘double-shot’ dose of 5Omg, as described in a preliminaty report [34]. These mAbs may represent an alternative to ATG or classic OKT3, although the data are far too preliminary for any conclusions to be drawn.

Fischer et al. [ 381 have successfully used a rat anti-CD1 la (25-3; IgGl) for the first time in children with inherited disease to prevent the rejection of bone-marrowmismatched haploidentical grafts. However, this was not reproducible in leukemic adult grafting with this mAb [39] or with an anti-CD18 mAb @chain> in another pilot study [40]. The anti-CDlla mAb appeared to be devoid of side effects, except for a transient fever after the first injection. We have tested the same mob in seven first kidney transplantations in the treatment of a first acute rejection episode [41]. This mAb mod&d the natural evolution of mild cellular rejection in only a single patient but could not reverse it in the other six patients, even when used at doses achieving ,high circulating lev els of mAb (120-180 mg over 10 days) in association with unmodified maintenance therapy (CsA-AZA). These con centrations are between three and twelvefold higher than the dissociation constant of this mAb (i.e. & -5nM), which suggests that this lack of effectiveness was not a consequence of drug concentration. Interestingly, the recipients showed an extremely low level of immunization against 25-3. Only one of the seven patients developed a low level of anti-25-3 IgG, at day 17. This may be related to the in vitro property of anti-CDlla to interfere with cell-cell interactions leading to antibody production. It is possible that this production is more sensitive to 25-3 than the immunological events leading to rejection. This property of anti-LEA-1 mAb, which was also observed in animals, raises the possibility of the induction of tolerance to other mAbs. Even though ln our experience antiCDlla was unsuccessful for the treatment of acute cellular rejection in kidney transplantation, the results obtained with bone marrow transplant recipients suggest that further studies may be interesting, particularly in prophylaxis protocols.

Another approach may be to use F(ab’)2 fragments. In mice, the F(ab’)2 fragment of 145 2Cll (murine equivalent of 0KT3) did not cause T-cell activation or increase the morbidity/mortality rate, although the survival of skin allografts was prolonged. This remains to be demonstrated in humans, however [35-J. Anti-LFA-1 mAb Cell-cell interactions through a variety of molecules ex-

pressed on the membrane surface between immunoreactive cells and their targets are necessaty for obtaining an optimum immune response. Among these molecules, members of the integrln family are involved in the early adhesion process. They have in common a structure composed of two non-covalently linked polypeptide chains (for review, see [36]). Three subfamilies are delined according to at least three different @-chains, and of these, CD18, which can associate with three different a-chains (CDlla, CDllb and CDllc), binds CDllc to form p150/95, CDllb to form Mac l/CR3, and CDlla to form the lymphocyte function-associated antigen @!A)-1 molecule. These three molecules are expressed only on leukocytes whereas their ligands, intercellular adhesion molecule (ICAM)-l and ICAM-2, are widely distributed. LEA-1 ligands are present on endothelial vascular cells, macrophages, monocytes and activated B lymphocytes. They are upregulated by TNl-a, IL-2 and IFN-y and can also be induced on fibroblasts, keratinocytes and epithelial cells. LEA-1 was first defined by anti-CDlla mAbs that inhibited cell-cell adhesion and effector functions in vitro including cytotoxlc T-lymphocyte activity, NK lysis, T-B-cell cooperation leading to antibody production, and T cell-monocyte and T-cell-vascular endothelial cell interactions. The cell-cell adhesion in which LFA-1 is involved enhances TCR-antigen recognition and provides auxiliaty signals for T-cell activation. T-cell activation also leads to an increase in cell ‘adhesiveness’ through con-

Anti-ICAMl mAbs have recently been tested in prlmates. R6.5, a mouse IgG2a, can delay the onset and reverse acute cellular allograft rejection episodes of kidney and heart allografts in cynomolgus recipients [42]. Two points are particularly interesting: anti-ICAM- mAb triggered an immune response in the primate, and the kidney endothelial cells were covered by mAb in treated animals, although the function of the graft was unimpaired and the histological examination did not show vascularltis. A clinical study has been initiated recently in man (B Cosimi, personal communication). One anti-CD2-mAb is also undergoing evaluation in association with anti-CDlla in bone marrow transplant seems to give encouraging results (in eight of nine patients no rejection at 1.5-6 months; A Fischer, personal communlcation). Anti-T12 mAb The anti-T12 mAb is a 120kD glycoprotein present on

the cell-surface membrane of post-thymlc T cells. It was one of the very first mAbs tested in a clinical trial [43].

Use of monoclonal antibodies in human transplantation Dantal and Soulillou

Whenusedat200ugkg-1perdayfor10daysthisIgM mAb resulted in regression of some mild rejection episodes but did not appear to have a better effect than conventional therapy. The sequential monitoring of PBL showed a decrease in T12 + cells immediately after the initial infusion, followed by the reappearance of T12 CD3+ cells after 2 or 3 days of anti-T12 treatment. This obsetvation suggests that mAbs that do not destroy the immunocompetent cells are ineffective in practice unless they are directed against antigens involved in important T-cell function. Anti-CD7 mAb CD7 is present on all T lymphocytes including thymocytes, but so far no function has been clearly assigned to this molecule. It has been suggested that this molecule might be involved in some T-cell activation pathway, as anti-CD7 n-&s can deliver an accessory signal to costim ulate T lymphocytes. RFT2, a mouse IgG2a anti-CD7 mAb, has been tested recently in human kidney transplantation. In association with CsA and corticosteroids [44] used at 5 mg daily from day 2 to day 12, it was unable to halt ongoing rejection episodes. However, this first series of trials was too small to give significant results and additional data are expected from a multicenter trial using a chime& anti-CD7 mAb [45] (a construct from the RFT2 hybridoma, and an Fc fragment from human &Cl). In vitro it shows an improved antibody-dependent cellular cytotoxicity, compared with RFT2, as well as a prolonged half-life in the rhesus monkey [46]. The recently initiated multicentric prophylactic pilot study suggests that the chimerlc anti-CD7 mAb is devoid of important side effects, but it does not yet allow any conclusion as to its possible clinical efficacy [45]. However, the authors reported no rejection episodes during the treatment of 11 patients with this anti-CD7 mAb and, in addition, this chimeric mAb did not elicit immunization (P Sweny, personal communication).

Campath 1 The rat IgM mAb, Campath 1, recognizes more than 95%

of peripheral mononuclear cells and is effective in T-cell depletion of bone marrow grafts. Campath 1 is also effective at 50mg day-l (for 10 days) in a prophylactic or a curative protocol in kidney rejection, probably because of its strong capacity for complement-mediated killing. However, a high incidence of infection was reported with an unacceptable proportion of life-threatening infection (15%), which led the authors of the report not to recommend it for routine use [47]. Anti-CD4 mAb

AntiL3T4 (the equivalent of anti-CD4 mAb in rodents) is able to prolong skin or cardiac allografts and to induce tolerance in the recipient when large doses are injected at the time of grafting 1481. Tolerance was obtained for the non-idiotypic determinant of the mAb itself, as well as for other xenogenic determinants. The anti-CD4 mAb family comprises a heterogeneous cluster in terms of in vivo efficiency, and their mechanisms of action remain un-

known (some mAbs delete the CD4+ T-cell subset, e.g. WT4, whereas others, which are less efficient, do not). They can inhibit the interaction between CD4 and class II MHC antigens, or alternatively transduce negative signals through the CD4 molecule. In the rhesus monkey, anti-CD4 mAbs (OKT3 and OKT4A) were able to suppress acute graft rejection in untransfused recipients of kidney transplantation [49], but not in transfused recipients [ 501. In addition, this anti-CD4 mAb did not result in the blockade of the immune response to its own determinant, even when used at high dosage. Recently, anti-CD4 (BL4; IgG2a) was administered immediately after kidney transplantation in human for up to 314 days [51]. Although this series was too limited to allow any definitive conclusions to be made concerning the potential BL4 effect on the incidence of early rejection (four episodes in 12 patients), only one patient developed anti-BL4 antibodies, suggesting that some anti-CD4 antibodies can mimic in man what was observed in rats [52]. mAbs targeting

activated

T cells

After antigenic challenge through the TCR, committed resting T cells become activated, secrete IL-2 and transiently express high-alfinity IL-2 receptor molecules (IL-2R), allowing these T cells toexpand in an autocrine pathway (for a review see [ 531). The distribution of this receptor is not absolutely restricted to T lymphocytes as it is also present on activated B cells and monocytes. The highalhnity IL-2R comprises at least two molecular components (a third has been described recently [ 541). The a-chain (P55 or Tat) is the inducible structure of the highaffinity IL-2R. P55 alone has only a low-affinity for IL-2 (& 2OnhQ, is not internalized and does not transduce a mitotic signal. The more recently characterized P-chain (P75) is able to internalize IL-2, has an intermediate affinity for IL-2 (Q = 1 r&I), and facilitates signal transduction. Distinct IL-2 domains interact with P55 and P75 to form h&h-afhity (Q = 2OpM) liganckeceptor complexes. Some authors have identified high-afhnity IL2R complexes in the absence of IL-2, but recent experimental studies favour a dissociated model where P55 rapidly binds IL-2 and interacts with P75, which alone would bind IL-2 at a much lower rate. All mAbs directed at the IL-2-binding site of the u-chain are potent inhibitors of IL-2-driven proliferation and are effective in in vivo models of skin, heart and kidney transplantation in rodents and primates (for a review see [ 551). They also prevent delayed-type hypersensitivity and auto-immune diseases. Their mechanisms of action, however, remain unclear, and at least two models have been proposed. First, IL-2R+ cells that are cleared from the circulation may be destroyed. For example M7/20 or 2E4 mAbs exhibit a strong complement-mediated cytotoxicity (CMC) [56,57] but in man, 33B3.1, which is effective in kidney transplantation (see below), does not induce CMC or antibody-dependent cytotoxicity. Second, only a direct interaction with the IL-2-binding site on P55 may be involved as it seems that only targeting of epitopes close to the IL-2-binding site are required for ob-

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taining in vivo immunosuppression (even if this is not always sufficient; e.g. lHT4-4H3 mAb in the monkey [ 581). In 1987, we reported a clinical study using a rat IgG2a anti-P55 mAb [59]. This mAb belongs to a cluster able to inhibit IL-2 binding on both P55 and high-affinity IL-2R and to block IL-2-driven proliferation. We showed that this mAb (33B3.1) used at 1Omg day-l for 14 days starting immediately after transplantation was with out side effects and is associated with a low incidence of rejection compared with that observed in an ATG historical group. A prospective randomized trial was then conducted in a prophylactic protocol. This study included 100 consecutive first cadaveric kidney transplantation in which 33B3.1 was compared with ATG [&?*I. The 33B3.1 mAb was administered (10 mg day-1 in a peripheral vein for 10 min) during the first 2 weeks after grafting in association with 1 mg kg-l per day of corticosteriod (decreased weekly and interrupted between day 30 and 45), 2 mg kg- l per day of CS (decreased weekly and interrupted between day 30 and 45), and 2mg kg-1 per day of AZ4 (adjusted according to haematological tolerance and withdrawn between day 30 and 45). CsAwas administered from day 14 (8 mg kg- 1 per day) and adjusted to the trough-whole-blood level. This study conlimred the absence of side effects of the mAb and a low incidence of rejection at 3 months (26% in the mAb group versus 31% in the ATG group). Early rejection episodes were more numerous than in the ATG group (12% versus 2% at day 15) and graft survival was the same in both groups at 1 and 2 years (85% and 81%, respectively) although patients treated with 33B3.1 presented less infectious episodes. The same mob is now under study comparison with ATG in a second kidney transplantation group (M Hourmant, personal communication) and a combined kidney/pancreas transplantation group (D Cantarovich, personal communication). Although these studies are not yet completed, the results seem to conlirm the efficacy of 33B3.1 in two clinical conditions; preimmunized (secondary grafts) and mismatched recipients (kidney/pancreas). However, reversible acute rejection episodes have been more numerous in the 3383.1 group than in the ATG group during the first 2 weeks after transplantation. Interestingly, results are very encouraging in double kidney/pancreas grafts in which the protocol included an association with CsA immediately after transplantation. Although during 33B3.1 treatment a signilicant decrease in the total lymphocyte count was observed (50% versus 78% with ATG), with a return to normal values at the end of the mAb course, the effect lasted 2 months in the ATG group. The early drop in the lymphocyte counts may not be caused by 33B3.1 but by the coadministration of corticosteroid 1611. Furthem-tore, no CD25+ cells could be detected during the mAb administration, suggesting that no expansion of activated T lymphocytes had occurred. 33B3.1 was strongly immunogenic; 80% of patients had detectable 1gM and/or IgG anti-mAb at day 20 (45% of them during treatment). Anti-idiotypic antibodies were al most always observed, although later than anti-isotype an tibodies. Neither 33B3.1 levels nor the anti-mAb response

directly predicted the timing and the occurrence of acute rejection, but rather anti-33B3.1 antibodies seemed to be related to the ‘high responsiveness’ of the patient. 33B3.1 was not found to be reliable in the treatment of ongoing acute kidney rejection (at 10 mg per day for 10 days) [6l]. Two out of the 10 patients that we have treated responded immediately, but the others needed rescue treatment by a bolus of corticosteroid, or had increased graft function only after reintroduction of corticosteroid orally. This was observed despite a high level of circulating 33B3.1. It is possible that IL-2R+ cells are not directly involved in the late stage of the rejection process, when the majority of inliltrating cells are represented by monocytes and macrophages or uncommitted T cells. Other anti-P55 mAbs are currently being tested. The studies are either incomplete or involve a small number of patients. The first experience with anti-Tat was associated with an unacceptably high incidence of acute rejection without CsA. However, positive results were reported in a randomized study with a murine anti-IL-2R mAb (antiTat; IgG2a) administered in a prophylactic protocol with CsA, compared with a similar regimen without anti-Tat. Various other mAbs are under investigation, including Lo Tacl (IgG2b) and BBlO (IgGl), but more information must be obtained in order to allow some conclusions to be made concerning the role of the epitope recognized > and the isotype involved. Comments Although ATG has been well recognized as being effective in the treatment of rejection, several disadvantages are associated with the use of polyclonal sera. These include variability among batches, reactivity with antigens unrelated to the lymphocytes and serum sickness. Therapy with mAbs should circumvent these problems by providing a single defined specificity, a unique target, the possibility of low dosage to obtain an effective concentration (no serum sickness) and the possibility of specific monitoring. The use of mAbs in prophylaxis is of major importance in allowing the prevention of the recipient immune response during the first days after transplantation. This allows the introduction of CsA in kidney transplantation to be delayed until stable graft function has been achieved. Most mAbs are targeted at all T lymphocytes (as ALG is) irrespective of the specific allorecognition determined by the TCR. 0KT3 is very powerful but its use is limited by a risk of over immunosuppression when administered to patients without high immunological risk (e.g. first graft in a non-responding patient), with an associated increase in infectious episodes and with a risk of lymphoproliferative disorders. It also has some important side effects, which cannot be prevented by the use of high doses of corticosteroid (increasing the immunosuppression) without unpleasant consequences. The new generation of anti-TCR arj3-mAbs that do not stimulate T cells may help to circumvent these side effects. Another approach discriminates against committed antidonor cells (less than 1% of the total lymphocyte pool

Use of monoclonal antibodiesin human transplantationDantal and Soulillou

as assessed by a limiting dilution assay). Under normal conditions, donor tissue antigens are the major stimulus after transplantation. L2R (P55) is a good target candidate ln thls strategy as it is only expressed after antlgenie stimulation in the first steps of the clonal expansion of alloreactive cells. In practice, it seems that this ‘anti-donor specificity’is indeed operational as shown by the first clinical studies using 33B3.1. Although the graft could carry over infectious agents (cytomegalovirus for example>, we have never observed life threatening cytomegalovirus infections with this therapeutic approach. Other means of IL-2R targeting have been studied in animals, and prellminaty studies are in progress in patients with autoimmune disease. Strom and colleagues 1621 have obtained novel targeting molecules by gene fusion. One of the genes used corresponds to the ligand (IL-21 and the other to a bacterial toxin (diphtheria, pseudomonas or shigella toxin). This fusion protein has a high-alhnity for IG2R, is internalized after binding to high affinity IL-2R, and after an initial, but transient, cell activation, kills the target cells. This anti-IL-2 toxin has been shown to inhibit delayed-type hypersensitivity reaction and to prolong graft survival in rodents [63]. No published data are yet available in primates (or in man> about its effectiveness in graft recipients and the incidence of patient immunization against the toxin compound. A combination of two mAbs (anti-P55 combined with anti-P75 [64]) targeted at IL-2R produced a synergistic effect in vitro [65*]. Such a combination of the two mAbs may be more effective on high-affinity IL-2R+ cells in clinical practice. Soluble truncated forms of cytokine receptors (the extracellular part of lym phokine receptors) have been shown to prolong heart allograft in mice (soluble IL-1 receptor [66] ; soluble-IL-4 receptor [67] 1. We are also studying a chimeric molecule made by a fusion of IL2 and human IgM. This fusion molecule has recently been shown to be cytotoxic for Tcell lines expressing HIA-IL-2R(R Breathnach et al., personal communication). Other possibilities arise from the observation that certain m&s, such as LFA-1or anti-CD4 may not be immunogenic . If it is proved by further studies that they are not powerful when used alone, these mAbs may be of interest in association with other immunogenically effective rnAbs. Finally, chimeric or humanized mAbs are likely to be of great interest for use in decreasing recipient immunization against mAb xenodeterminants. In the course of ongoing rejection, the general strategy encounters problems that are likely to be of a completely different nature. Clonally expanding T lymphocytes accumulate in the rejecting graft and recruit many uncommitted effector cells (monocytes/macrophages) that represent the majority of graft-inliltrating cells. At this stage, targeting of donor-committed cells may be insufficient, as shown by the 33B3.1 study [ 591, and efficient immunointervention may require interaction with all lymphocytes and with immunocompetent cells including nonlymphoid cells (by 0KT3, anti-TCR mAb, ATG). Fll, the cost of the new strategies offered by bioreagents is high. They are nevertheless a promising tool

their efficacy needs to be carefully explored in clinical trials. These clinical trials are needed to define the molecules that will, in the future, be the targets of choice in lmmuno-intervention. Moreover, these new molecules (rnAbs, chimerlc or humanized mAbs, chime&z proteins and artificial antagonist molecules) may lead to an ‘intelligent’ and specllic targeting and represent the tools that will be used in the clinic. and

Acknowledgement We are grateful to MS Aline Bertho for excellent secretarial assistance.

References and recommended reading Papers of special interest, published within the annual period of review, have been highlighted as: . of interest .. of outstanding interest 1.

MONACOAP, WOOD ML, Ru~.?ELPS: Some Eikcts of Purified Heterologous Antihuman Lymphocyte Serum in Man. Trun@nkatkm 1%7, 5:110&1111.

2.

HO~XMAAJ, VANLIERHJJ, REEKERSP, KOENE RAF? Improved patient and Graft SurvivaI After Treatment of Acute Rejections of Cadaveric Renai AIiograft with Rabbit Antithymocyte Globuhn. Trarq&nkation 1985, 39:27&80.

3.

Touw Jl, Bou E, EL YAFI S: Infectious LymphoproRferative Syndrome in Transplant Patients under Immunosuppressive Treatment. Trunspkant Proc 1985, 1796-98.

4.

ORTHOMULTICE~R TRANSPIANT STUDYGROUP:A Randomized Clinical Trial of OKT3 Monoclonai Antt’body for Acute Rejection of Cadaveric Renal Transplant. N En@ J Med 1985, 313:337-341.

5.

COSIMIAB, BURTONRC, COLVINB, GOLDSTEIN G, DELMONICO FL, IAQUAGLLA MP, Torxo~+Ruam N, RUBINRH, HERRINJT, RUSSELPS: Treatment of acute Renai AUograft Rejection with 0KT3 Monoclonai Antibody. Trurq&nkation 1981, 32:535-539.

6.

VIGERAL P, CHKOFFN, CHATENOUD L, CAMPOSH, IACOURBEM, DROZ D, GODSTEING, BACHJF, KREISH: ProphyIactic Use of

0KT3 Monoclonai Antibody in Cadaver Kidney Recipients. TranSphnkztion 1986, 41:73&733. 7.

BENVENISIY AI, COHEND, STEGAUMD, HARDYMA Improved Results Using 0KT3 as Induction Immunosuppression in Renai AIIograft Recipients with Delayed GraR Function. TranqSantation 1990, 49:321-327.

8.

OH CS, SOLLINGER HW, STRA~TARJ, KAL~YOUGLU M, BEIZER FO: Delayed Response to Orthoclone 0KT3 Treatment for

RenaI ARograft Rejection Resistant to Steroid and Anti-Lym phocyte GlobuRn. Tran@antution 1988, 45:65-67. 9.

Hrucnc DE, ZARCOMJ, SCHUIAKJA: Influence of Low-Dose Cyclosporine on the Outcome of Treatment with 0KT3 for Acute Renal AIiograft Rejection. Tran.pkaniation 1989, 47:272-277.

10

RINLUNDDG, O’CONNELIJB,

GUBERT EM, HAMMONDME, BURTONNA, JONESKW, KARWANDE SV, Don DB, MENUXE RI, HEKRICKCM, ET AL: A Prospective Comparison of Murine

MonoclonaI CD-3 (OKT3) Antii-Based and Equine Antithymocyte Glob&n-Based Rejection ProphyIaxis in Cardiac Transplantation. Tratyphntution 1989, 47:599-605. 11

FIZEYDJ, MATA~AJ, GILUNGHAM KJ, CANAFAXD, PAYNEWD, DUNN DC, SUTHERIAM)DER, mJARL4NJJ: MALG vs 0KT3 Fogowing Renai TranspIantation: a Randomized Prospective Trial. Tran.pkmt Pm 1991, 23:1048-1049.

745

746

Transdantation 12.

NORMAN DJ, Bm JM, BEwrr WM, MUNSON JC, IMF(ERM, HENEU K, KIMBALL J, HUBERTB: 0KT3 for Induction Immunosuppression in Renal TranspIantation. A Comparative Study of High Versus Low Doses. Trarqihnt

Proc 1991,

23:1052-1054.

13.

CHANGTW, KING PC, GINGRAYSP, Gommuu

27.

CHATENOUD L, JONKERM, V~MAIN F, Gom~rn G, BACHJp: The Human Immune Response to the 0KT3 Monoclonal Antibody is OUgoclonal. Science 1986, 232:1406-1408.

28.

SCHROEDER TJ, FIRST m MANSOURME, HLJRTUB~~E PE, m S, RYCKMANFC, MLINDA R, MELVIN DB, PENN I, BAUISTREIUWF, AIJZXAM~ER YJV Antiimmune Antibody For-

G: Does OKT3

mation FoRowing 0KT3 4948-51.

Monoclonal Antibody React with an Antigen Recognition Structure on Human T Cells. Proc Nat1 Acad Sci USA 1981, 78:180>1808.

14.

29.

CHATENOLJD L, BAUDRIHAYE MF, KREIs H, GOLDSTEIN G, SCALER J, BACHJF: Human In vfvo Antigenic Modulation

Induce& by the Anti T-Cell OKT3 Eur J Immund 1982, 12;979--984. 15.

16.

17.

18.

30.

1989, 48:3%36.

CAILIAT-ZUCA$AN S, BLUMENFELD N, LEGENDRE C, NOELLH, BACH JF, KREIsH, CHATENOUD L The 0KT3 Immunosuppressive Effect. In Situ Antigenic Modulation of Human Graft Intiltrating T Cells. Tran.@untatzbn 1990, 49:156160. CHAUHANB, MOHANAKUMAR T, WA= FLVE M: Immunohistological Analysis of T Lymphocyte Subpopulation in Needle Core Biopsies from 0KT3 Treated Renal Allograft Recipients. Tranqhntation 1990, 50:1058-1060. G~U%TEIN G, NORMALDJ, HENEU KR, S~VIITH IL: Pharmacokinetic Study of Orthoclone 0KT3 Serum Levels During

Treatment

of Acute RenaI Allograft Rejection.

31. .

20.

CHATENOUD

21.

L, FERRAN C, LEGENDRE C, ~OUARD 1, MEm S, REUIZRP+ GEVAERT Y, KREIs H, FRANCHIMON TP, BACHJF: In Viva Cell Activation Following OKT3 Administration: Septemic Cytokine Release and Modulation by Corticostcroid. Tran.#antution 1990, 49697-702.

22.

23.

24. ..

WONGJT, EYLATH AA, GHOBR~AL I, COLT RB: The Mechanism of Anti CD3 Monoclonal Antibodies. Mediation of Cytolysis by Inter-T Cell Bridging. Tran.@wz&ztion 1990, 50:68W9. C, Dy M, MEm S, SHEEHANK, SCHREIBER R, LEBOUIENGER F, IAMlAlsP, GLUESTO~J, BACHJF, CHATENOUD L Reduction of Morbidity and Cytokine Release in AntiCD3 Tranqkmtation MoAb Treated Mice by Corticosteroids. 1990, 50642-648.

FEW

CHATENOUD L, IEGEND~ C, FERRAN C, BACHJF, KREisH: Corticosteroid Inhibition of the 0KT3 Induced Cytokine-Related Syndrome. Dosage and Kinetics Prerequisites. Traryplanradon 1991, 513334-338.

tier several publications on lyrnphokine release following 0KT3 treatment, this paper reports a prospective randomized trial to deline the best schedule of corticosteroid administration in association with the first 0KT3 injection to prevent OKT3 side effects. FERRAN C, SHEEHAN K, %HIEIBERR, BACH JF, CHATENOUD L: . Antibody Significantly Abrogates the Anti-TNF Monoclonal Anti CD3 Induced Reaction. Traqthnt Proc 1991, in press. This paper demonstrates the involement of TNF in the anti-CD3 reac25.

GOLDMANM, -M JL, ABRAMOWICZ D, DE PAUV L, KINNAERT P, VEREERSI‘RAETE N P: Evolution of Renal Function During

Treatment of Kidney GraR Rejection with 0KT3 Monoclonal Antibody. Tran.@kxntatim 1990, 50:15%159.

SWINNEN LJ, COSTANZO-NORDINMR, FISHER SG, O’SULWAN EJ,

JOH~%ONMR, HEROUXAL, Dms GJ, PIFM~RE R, &HER RH: Increased Incidence of Lymphoproliferative Disorder

32.

FRENKEN IAM, Homhw AJ, TM WJM, KOENERAP: Prophylactic Use of Anti CD3 Monoclonal Antibody m32 in Kidney Transplantation. Tran.@ant Proc 1991, 23:1072-1073.

33.

WAN TH,

.

Lucx BA, THOMPSON JS, MUNCHLC, BROWNS, Kwsc~o R, PREBECKR, VAN HOY MA, JEZEKD: Treatment of Acute Rejection with Anti T Cell Antigen Receptor Complex Alpha Beta (TlO B9 lA-31) or Anti CD3 (OKT3) MonoclonaI Antibody. Results of a Prospective Randomized

Double Blind Trial. TranqDhnt

Pruc 1991, 23:1062-1065.

First results of

a prospective randomized trial in kidney tmnsplantation with a new anti-TCR mAb. 34.

IANDW, MUBRANDG, ILLNER WD, ABENDROTH D, HANCKEE, S~HLE~BNERE S, HAMMER C, RACENBERG J: First CIinical Experience with a New TCR/CD3-Monoclonai Antii (BMA 031) in Kidney Transplant Patients. Tranqhnt Int 1988, 1:116117.

35. .

HIRXH R, BLUESTONE JA, DENENNO L, GRESS RE: Anti CD3 F(ab’)Z Fragments are Immunosuppressive In Viva Without

Evoking Either the Strong Humoral Response or Morbidity Associated with MoAb. Trangkzntatbn 1990, 49:1117-1123. This study suggests that in mouse the use of F(ab’)Z fragments of anti CD3 mAb does not induce ‘OKT3 syndrome’, although these fragments are able to delay skin graft rejection. 36.

SPRINGER TA: Adhesion Receptors Nature 1990, 346:425-434.

37.

HEAGYW, WALTENBAUGH C, MAwrzE: Patent Ability of AntiLFA-1 Monoclonal Antibody to Prolong Allograft SurvivaL

38.

FISCHER A, GRIXELIJ

Trarqhntution

of the Immune System.

1984, 37:520-523.

C, BUUVCHES, LE DEIST F, VEBER F, LOPEZ M, DELUGE M, OLIVE D, MwAs C, Jmosst’ G: Prevention

of Graft FaiIure by an Anti LFA-1 Monoclonal Antibody in HIA-Mismatched Bone Marrow Transplantation.Luncet 1986, 39.

i&1058-1061.

MARhMNcm D, MAWASC, STOPPA AM, GASPARDMH, m G, EKTHOVEN H, REIFFEE JI, OLIVED, m M, DEL~AGE M, ET

AL:Anti-LFA-1 Monoclonal Antii

for the Prevention of Graft Rejection After T Cell-Depleted HLA-matched Bone Marrow Transplantationfor Leukemia in Adults. Bone Marrow Trar@ant 1989, 4:147-150.

tion. 26.

OH CS, STRA?TA RJ, Fox BC, SOI~INGER HW, BELZER FO, m DG: Increased Infections Associated with the Use of OKT3 for Treatment of Steroid-Resistant Rejection in Renal Trans1988, 4568-73. plantation. Tran.@zntation

reports a sharp increase in the ineidence of post-tramplantation lymphoproliferative disorders among the cardiac transplant recipients using OKT3, and prompts a reassessment of the 0KT3 risk/benefits.

CHATENOUD L, F!xuw C, IZGENDRE C, RENTER A, FRANCHIMONT P, KREIsH, BACHJF: Clinical Use of OKT3: the Role of Cytokine Release and Xenosensitization. J Autoimmunity 1988, 1:631-&l.

HIRSCHR, CHATENOUD L, Gaixss RE, SACHSDH, BACHJF, BLUESTONE JA: Suppression of the Humoral Response to Anti CD3 Monoclonal Antibody. Tran.@antation 1989,

This paper

kztion 1988, 46:587-589.

Tmsm~xnwm JR, GABER AO, HAAG BW, ARONON AJ, BROEISCHCE, STUART JR, STUART FP: 0KT3 Treatment of Steroid-Resistant Renal Mograft Rejection. Tranqhntation 1987, 43:17&184.

1990,

After hnmunosuppression with the Monoclonai Antibody OKT3 in Cardiac-TransplantRecipients. N Engl J Med 1990, 3231723-1728.

Tran@an-

19.

Tran.@zntatkm

47~85-57.

Monoclonal Antibody.

KERRPG, Ams RC: The Effects of OKT3 Therapy on Inliltrating Lymphocytes in Rejecting Renal Allografts. Tram pkantution

Therapy.

40.

BAUMED, KUENIZ M, PICO JL, BWUJMN F, CORD~NNIERC, VERNANT JP, HAYAT M, BERNARD A: Failwe of a CD18/anti-LFA1 Monoclonal Antibody Infusion to Prevent Graft Rejection

Use of monoclonal antibodiesin human transplantationDantal and Soulillou Immunosuppressive Management of Kidney Graft Recipients. Tratqhnt Reviews 1990, 4:7F92.

in Leukemic Patients Receiving T-Depleted AIlogeneic Bone Marrow TranspIantation. Tran@zatation 1989, 471472474. 41.

k MAW B, How&w-r M, ROUGIER JP, HORNM, DANTALJ, BAATARDR, CANTAROQCHD, JACQUES Y, Souuwu JP: Effect

56.

of Anti-LFA-1 (CDlla) Monoclonal Antibodies in Acute Rejection in Human Kidney Transplantation. TranSphntation 1991, in press.

JP: Cluster-Function Relationship of Rat Anti-Mouse p55 ILZ-Receptor Monoclonal Antibodies. In Vfh Studies on the CTL-L2 Mouse CelI Line DANTAL J, JACQUESY, Souwu

and In Vivo Studies In a Delayed m Hypersensitivity Model in Mice. Tran.pkzntation 1991, 52:110-115.

42.

COSIMIAB, Corn D, DELMOMCO FL PREFFERFl, WEE SI, ROTHLENR F-s R, Co~vw RB: In Vivo Effects of Monoclonal AntIbodies to ICAM- (CD54) in Non-Human Primates with RenaI AIlogra%. J Immund 1990,144:4604-%12.

57.

KEL~FYVE, GAULTON GN, STROMTB: Inhibitory Effects of Anti-Interleukin 2 Receptor and Anti-L3T4 Antlbodles on Delayed m Hypersensitivi~ the Role of Complement and Epitope. J Immund 1987, 13:2771-2775.

43.

w

RL, ARAUJO JL, BUSCH GJ, CARPE CB, MILFORD EJ_ REINHE%!EL, Scmsw SF, STROMTB, ‘IlllrlFI NL: Treatment

58.

RL, REED MH, Puss JD, MAzouJlAN SHAPIROME, KIRKMAN G, LETVINNL, CARPENTER CB, MLLFoRDEL, WALDMANN TA, STROMTB, SCHU%SMAN SF: Monoclonal Anti ILZ-R Antibody in Primate Renal Transplantation. Tranplant Proc 1987, 19:594-598.

of Acute AIIognft Rejection with Monoclonal Anti-T12 Antibodies. Tranqblantation 1983, 36:6213626. 44.

45.

FRY MJ, LANGCJ, IVORYK, TIDRANN, SWENV P, FERNANDO ON, MOORHWD JF, JANOSSV G: Use of m2 (CD7) Monoclonal Antibody as Prophylaxis Against Renal Allograft Rejection. Trampkant Pnx 1985, 17~2737-2739.

SWEEY P, AMLOT P, FRENANIX 0, HEINRICH G,Gkw H, SCHREIER M, ARDENJONES M, Moo= J: Pilot Study of Chimerlc Human/Mouse CD7 Monoclonal Antibody (SD2 CMH 380) ln Renal Transplantation. Transplant Prcc 1991, in press.

46.

HEI~XH G, Gm H, KOCHERHP, SCHEEIER MH, RYFFELB, OESTBERG L, mm A, AMIOTPL, JANOSSV G: Characterization of a Human T Cell Specilic Chimeric Antibody (CD7) with Human Constant and Mouse Variable Regions. J Immunol 1989, 143:358%3597.

47.

WALDMAMV H, GORE S, THIRU S, Jovs~l V, EVANSDB, CALNERY: Campath-1M Prophylactic Use of After

FRIENDPJ, m

G,

59.

S~UL~LLOU JP, PF(RONNET P, LE MAUFFB, HOURMANT M, OUVE D, MAWAS C, DE~MGEM, JACQUES Y: Prevention of Rejection of Kidney Transplants by MonoclonaI AntIbody Directed Against Interleukin 2 Receptor. funcet 1987, i:133+1342.

60. ..

SOUULLOU JP, CANTAROVICH D, LE MAUFF B, Gw M, HOURMANT M, HIRNM, JACQUESY: Randomized Trial of an Anti-Interleukin 2 Receptor Monoclonal Antibody (33B3.1)

Versus Rabbit Antithymocyte Globulin (ATG) in Prophylaxis of Early Rejection ln Human Renal Transplantation. N En@ J Med 1990, 322:117~1182.

The first large randomized frial of an anti-IL-2 receptor mAb in prophylaxis of rejection in kidney transplantation showing the same results as ATG 61.

Kldney Transplantation. A Randomized Controlled Clinical Trial. Tramphtation 1989, 48:248-253.

48.

49.

BENJAMIN RJ, Qm S, WISEP, COBBO~ SP, WALDMANN H: Mechanisms of Monoclonai Antibody-Facilitated Tolerance Induction: a Possible Role for the CD4 (L3T4) and CD1 la (LFAl) Molecules in Self-Non-Self Discrimination. Eur J Immunol 1988, 18:107!+1088. Cosl~l B, DELMOMCO FL, WRIGHT JK, WEESC, PREFFER F, BEDLE M, COLVLN RB: OKT4 Monoclonal Antibody Immunosuppression of Cynomolgies Renal Allograft Recipients. Tran.plant Pnx: 1991, 23:501-503.

50.

51.

52.

PEARSON TC, ~~AGSEN JC, WOODKJ: Effect of Anti-CD4 MonoclonaI Antibody Dosage When Combined with Donor Antigen for the Induction of Transplantation Tolerance. Trans plant Proc 1991, 23:56+566. MORELP, VINCENTC, CORDERG, PANAGEG, CARO~EUA E, REvrw JP: Anti CD4 Monoclonal Antibody Administration in Renal Transplanted Patients. Clin Immunof Immunopathol 1990, 56:311-322. SHIZURU JA, SEY~EL KB, Fuw TF, Wu AP, KONGCC, HOYT EG, FUJIMOTONM BILUNGHAM ME, STARNES VA, FATHMAN CG: Induction of Donor Specllic Unresponsiveness to Cardiac Allograft in Rats by Pretreatment anti-CD4 Monoclonal Antlbody Therapy. Tran.pkantation 1990, 50:366-373.

53.

SOUlrLtoUJP, CANTAROMCH D, DANTAL J, HOURMANT M, LE Mwm B, JACQUES Y: Anti-IL2 Receptor and Anti-LFAl MonocIonal Antibodies in Transplantation: Rationale and Names Clinical Experience. CRC Press Inc 1991, in press.

54.

COmdOrWl OR, NECKERS LM, ROSOLEN A: Putative Gamma Subunit of the IL2 Receptor is Detected in Low Intermediate, and High AIiInIty IL2 Receptors Bearing Cells. J Immunoll990, 146:155-160.

55.

LE MAUFFB, CANTAROVICH D, JACQUES Y, Souul~ou JP: Monoclonal Antibodies Against Interleukln-2 Receptors in the

CANTAROVICH D, LE MAUFFB, HOURMANT M, GIRALM, DENTS M, HORN M, JACQUES Y, Souuwu JP: Anti-Interleukln 2 Receptor Monoclonal Antibody in the Treatment of On-going Acute Rejection Episodes of Human Kldney Graft. A pilot Study. Traqiximtation 1989, 47:454-457.

62.

BACHAP, WILUAMS DP, WATERSC, WIII~AMS JM, MURPHY JR, STROMTB: Interleukln 2 Receptor-Targeted Cytotoxicity. Interleukin 2 Receptor-Mediated Action of a Diphtheria Toxin-Related Interleukin 2 Fusion Protein. J Exp Med 1988,

167:612~22. 63.

JC, Muww JR, KELLEV VE, BACHAP, PANKNWCZ0, NICHOLS STROMTB: Interleukin Z-Diphtheria Toxin can Abolish CeIlMediated Immunity In Vivo. Proc Natl Acad Sci CBA 1988, 85:398&3984.

64.

TSUDO M, Krrwu~~ F, MPI’ASAKA M: Characterization

of the Interleukin 2 Receptor Beta Chain Using Three Distinct Monoclonal Antibodies. Proc Nat1 Acud Sci USA 1989,

86:1982-1986. AUDRAIN M, BOEFFARD F, Souuwu JP, JACQUES Y: Synergistic Action of Monoclonal Antibodies Directed at p55 and p75 Chains of the Human ILZ-Receptor. J Immund 1991, 146:884892. Report on in w&o synergistic action of fwo anti-IL-2RmAbs, suggesting a promising way for IL-ZRtargeting in clinical human transplantation. 65. .

66.

FANSLOW WL, S~hls JE, SAssENF!ZmH, MORRISSFIPJ, GILL~S S, POWERSD, W~DMER MB: Regulation of Alloreactivity In Vivo by a Soluble Form of IL1 Receptor. 248~739742.

67.

Science 1990,

FANS~WW, CLIFFORD K, BECKMAN M, WIDMERM:

Regulation

of In Vivo Alloreactlvltles by IL4 and the Soluble IL4 Receptor. Tranpkznt Proc 1991, in press.

J Dantal and J-P SouliIlou, Service de N+hroIogie, Immunologic, CHU, Place Alexis Ricordeau, 44035 Nautes Cedex, France.

747