© 1991 Karger AG. Basel 0011-9075/91/183.VO 184 $ 2.75/0
Dermatologies 1991:183:184-186
Expression of Complement Receptor CR2 (CD21) on Human Subcorneal Keratinocytes in Normal and Diseased Skin ./.
Hunyadia, M. Simon Jr.b, A.Sz. K enderessyA . Dobozy''
“Departm ent of Dermatology. Albert Szent-Györgyi Medical University, Szeged. I lungary; '’Department of Dermatology, University of Erlangen-Nürnberg. Erlangen. FRO
Key Words. CD21 antigen • CR2 ■C3d receptor • Keratinocytes • Psoriasis • Skin diseases Abstract. Human keratinocytes are able to synthesize and express cell surface moieties characteristic of effector and/or accessory cells of the immune system (CD 16, CD36. HLA-DR. intercellular adhesion molecule-1). In the pres ent study, skin biopsies from healthy volunteers, from patients with psoriasis vulgaris (PV). mycosis fungoides (MF), purpura pigmentosa chronica (PPC), acute urticaria (AU) and from positive tuberculin skin tests were investigated with regard to the reactivity with the monoclonal antibodies to complement receptors CR 1CR2 and CR3 by means of a multistep immunoperoxidase method. In the clinically involved skin of all patients with PV. MF or PPC, and in biopsies obtained from positive tuberculin tests, specific epidermal intercellular staining with OKB7 and Leu anti-CR2 was seen on subcorneal keratinocytes. This finding suggests a differentiation-linked expression of CR2 on human keratinocytes in cytokine-mediated skin diseases whereas CR1 and CR3 arc apparently not expressed.
body Leu-1 lb (CD16), which is a typical marker of NK cells and granulocytes [6], and under certain circum stances (in different cytokine-mediated dermatoses such as mycosis fungoides (MF). psoriasis vulgaris (PV). purpura pigmentosa chronica (PPC), and in positive tu berculin skin tests, etc.) they also become HLA-DR-, HLA-DQ-, CD36- and intercellular adhesion molecule-1 (ICAM-l)-positivc [7, 8], To get further information on the surface character istics of HK, we investigated the expression of CR1, CR2 andCR3 in the epidermis of healthy volunteers and in that of patients with different dermatoses. The present study provides evidence that in the skin of patients with PV, MF or PPC and in biopsies obtained from positive tuberculin skin tests HK of the subcorneal cell layers specifically react with the monoclonal antibodies OKB7 (CD21) and Leu anti-CR2 (CD21). but not with those against CRI and CR3.
Materials and Methods Patients Investigations were carried out on surgical skin specimens from 10 healthy volunteers who underwent plastic-surgery, and on punch biopsy specimens (3 mm) of involved and uninvolved skin from patients with
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/7/2018 4:31:47 PM
Different cell types of the immune system possess spe cific receptors for complement fragments (CR). The bestcharacterized receptors for complement components arc those for the major split fragments of C3. CR1 (C3b receptor; CD35) is expressed on the surface of myeloid cells and has three major physiological functions: it is a cofactor for enzyme factor I in the cleavage of C3b to iC3b; it represents a receptor mediating endocytosis and phagocytosis of opsonized particles; and it participates in eliminating immune complexes and other cell particles bearingC3 and C4from the circulation [ 11. CR2 (CD21) is a receptor located on B lymphocytes, dendritic cells and nasopharyngeal epithelial cells [2—4]. Its ligands are C3d and the Epstein-Barr virus [5], The induction of B cell memory and of an efficient secondary response are pre sumed to be mediated through CR2 [ 1]. CR3 (CD 1lb) is a receptor for iC3b and for certain carbohydrate residues present on zymosan and beta-glucan particles. This recep tor is restricted to cells of the myeloid series and to natural killer (NK) cells. Ligation of this receptor may induce phagocytosis [1, 3). It is well known that human keratinocytes (HK) are able to express cell surface antigens characteristic of effector and/or accessory cells of the immune system. Thus, they specifically react with the monoclonal anti
CR2 Receptor on Subcorneal Kératinocytes
185
Fig. 1. CD21 expression on subcorneal human kératinocytes in involved psoriatic skin (a) and in tuberculin-positive skin (b). A EC X 400.
Immimohistochemistry 4-[im sections were cut on a cryostat and reactivity with monoclonal antibodies Leu anti-C R l. Leu anti-CR2. OKB7 and OKMI (table 1) was visualized by means of a multistep immunoperoxidase method described by Poppema et al. [9], Briefly, cryostat sections were frozen at -70 °C for at least 24—18 h. A fter thawing, they were immediately washed in phosphate-buffered saline (PBS). pH 7.2. and incubated with the monoclonal antibodies for 30 min at room temperature. The sections were subsequently washed 3 times in PBS and incubated with peroxidase-conjugated rabbit-antimouse antibody (Dakopatts. Glostrup. Denmark) diluted 1:10 with human AB serum diluted 1:1 with PBS (SPBS). This was followed by PBS washing and by a 30-min incu bation with peroxidase-conjugated swine-antirabbit antibody (D ako patts) diluted 1:10 with SPBS: After 3 w'ashcs with PBS. the specific peroxidase activity was revealed by usingaminoethyl carbazoie (A EC) as substrate, followed by a 10-min rinse in distilled water. Finally, counterstaining was performed with hemalum. Two kinds of negative con trols were included: firstly, omission of the primary monoclonal anti body and. secondly, substitution of the primary antibody with irrele vant antibodies (mouse monoclonal antibodies IgG, and IgG.a: Bccton Dickinson).
Results There was no specific positive staining as concerns CD35 (C R I) and CD 11b (CR3) expression on epidermal
Table 1. Murine monoclonal antibodies directed against human cell surface markers Antibody
CD
Protein content, ug/ml
Leu anti-C R l1 Leu anti-CR2‘ OKB72 O KM I2
CD35 CD21 CD21 CD 11b
6.25 1 10 2
1 2
CD = Cluster designation. Becton Dickinson. Mountain View', Calif.. USA. Ortho Diagnostics. Raritan. N.J.. USA.
cells (neither HK nor Langerhanscells) in specimens from the investigated persons, but in all skin biopsies from posi tive tuberculin reactions, from patients with PV, MF or PPC the dermal inflammatory infiltrate exhibited CD1 lb (CR3)- and CD35 (CR1 )-positive cells. On the other hand, in all biopsies from positive tuber culin reactions and from patients with PV, MF or PPC HK of the subcorneal cell layers exhibited a net-like specific positive staining when exposed to Leu anti-CR2 (CD21) (fig. 1) or OKB7 (CD21). No specific CD21-positive staining of FIK was observed in skin specimens of healthy volunteers, in those of patients with AU and in the clin ically uninvolved skin of patients with PV. MF. or PPC. In 4 of the 10 patients with PV, typical Munro abscesses containing CD35 (CR1)- and CD1 lb (CR3)positive leukocytes were revealed.
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/7/2018 4:31:47 PM
PV (n = 1()). MF stage II (n = 3). PPC (n = 3). acute urticaria (Au: n = 3) and on biopsies obtained from positive tuberculin skin tests (72 h after injection of purified protein derivate: n = 3 ). None of the patients had been involved in any systemic treatm ent or had used topical corti costeroids during the last 3 weeks before the biopsy. Each specimen was immediately frozen in liquid nitrogen.
■a
186
Hunyacli/Simon/Ketuleressy/Dobozy
The surface characteristics of different cell lines (such as T and B lymphocytes, monocytes/macrophages, etc.) constantly change during their differen tiation. Similarly, the expression of the surface moieties on I IK also reflects their stage of differentiation. Thus, the expression of CD 16 is detectable on the surface of basal HK in normal skin. In delayed-type hypersensi tivity reactions, the same antigen also appears on the surface of subcorneal HK. while cells of the stratum spinosum often remain negative or give only a weak positive intercellular reaction with the Leu-1 lb anti body. The intraepiderm al expression of CD36 in both delayed-type hypersensitivity reactions and in lichen planus is very similar to that of CD lb under the same clinical conditions [6, 7|. CR2 is a receptor located on B lymphocytes and den dritic cells (absent from CD 1-positive Langcrhans cells) |2. 3). Evidence of anti-CR2 reactivity of nasopharyngeal epithelial cells also exists [4|. C3d (35 kD). a degradation product of the third component of the complement, is the ligandof CR2. Several studies indicate that, in addition to C3d. CR2 also binds iC3b, C3dg and Epstein-Barr virus [5. 10]. CR2 enables B lymphocytes in areas distant from sites of inflammation to bind fragments of C3 in conjunc tion with immune complexes or bacterial particles. The induction of B cell memory and of efficient secondary responses is presumed to be mediated by this receptor [ 11]. The present study yields evidence that in biopsies obtained from tuberculin-positive skin and in those from the involved skin of patients with PV. M For PPC subcor neal HK specifically react with anti-CR2 monoclonal anti bodies. In contrast, the uninvolved skin of patients with PV. MF or PPC. both the involved and uninvolved skin of patients with AU. and skin specimens of healthy volun teers failed to display CD21 antigen. These findings sug gest that in a certain stage of differentiation HK. like human pharyngeal epithelial cells [4] and human B lymphocytes ¡12], may express CR2. The absence of CD21 antigen on subcorneal HK in skin specimens obtained from patients with acute urticaria suggests that CD21 expression of subcorneal HK might be con nected with cytokine-mediated skin reactions. Whether the acquired, presumedly not disease-specific, antiCD21 (CR2) reactivity of lesional HK in cytokine-medi ated skin diseases is due to C'R2 synthesis by HK. and whether it fulfils an immune function, remains to be eluci dated.
Acknowledgements The excellent tcehnical assistance of Miss W. Leisgang and Miss B. I iusslcin is gratefully acknowledged. This work was supported by grant Si 291/4-1 from the Deutsche Forsehungsgemei nscha ft.
References 1 Walport MJ. Lachmann PJ: Allergy, immune complexes and the complement cascade: in Lessof M il. Lee T H . Kemeny DM (eds): Allergy: An International Textbook. Chichester. Wiley. 1987. pp 217-236. 2 Weis JJ. Fearon DT. Kiekstein I.B. Wong WW. Richards SA. De Bruyn Kops A. Smith JA . Weis J 11. identification of a partial cDNA clone for the C3d/Epstein-Barr virus receptor of human B lymphocytes: Homology with the receptor for fragments C3b and C4b of the third and fourth components of complement. Proc Natl Acad Sei USA 1986:83:5639-5643. 3 Ross G D . Medof ME: Membrane complement receptors specific for bound fragments of C3. Adv Immunol 1985:37:217-267. 4 Young LS. Clark D. Sixbey JW. Rickinson AB: Epstein-Barr virus receptors on human pharyngeal epithelia. Lancet 19864:240-242. 5 Fingeroth JD . Weis JJ. Tedder TF. Stromingcr JL. Biro PA. Fea ron DT: Epstein-Barr virus receptor ofhum an B lymphocytes is the C3d receptor CR2. Proc Natl Acad Sci USA 1984:81:4510-4514. 6 Simon M Jr. Hunyadi J: Leu-1 lb (CD16) antigen expression on human kératinocytes. Arch Dermatol Res 1988:280:176-178. 7 Hunyadi J. Simon M Jr. Dobozy A: Immunologischc Bedeutung humancr Keratinocyten. Zcntralbl Haut 1990:157:673-685. 8 Simon M Jr. I leese A. Gôtz A: lmmunopathological investigations in purpura pigmentosa chronica. Acta Derm Venereol (Stockh) 1989:69:101-104. 9 Poppema S. Balm AK. Reinherz EL: Distribution of T-cell subsets in human lymph nodes. J Exp Med 1981:153:30-41. 10 R ossG D . LambrisJD: Identification of a C3bi-specific membrane complement receptor that is expressed on lymphocytes, mono cytes. neutrophils and erythrocytes. J Exp Med 1982:155:96-110. 11 Weis JJ.T oothaker LE. Smith J A. W cisJH . Fearon DT: Structure of the human B lymphocyte receptor for C3d and the Epstein-Barr virus and relatedness to other members of the family of C3/C4 bind ing proteins. J Exp Med 1988:167:1047-1066. 12 Tedder TF. Clement LT. Cooper MD: Expression of C3d receptors during human B cell differentiation: Immunofluorescence analysis with the I IB-5 monoclonal antibody. J Immmunol 1984:133: 678-683.
Received: June 18. 1990 Accepted: February 15. 1991 Dr. Janos I lunyadi Department of Dermatology Albert Szent-Gyorgyi Medical University, Szeged PO. Box 480 Szeged (Hungary)
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/7/2018 4:31:47 PM
Discussion
Dermatologies 1991:183:184-186
Expression of Complement Receptor CR2 (CD21) on Human Subcorneal Keratinocytes in Normal and Diseased Skin ./.
Hunyadia, M. Simon Jr.b, A.Sz. K enderessyA . Dobozy''
“Departm ent of Dermatology. Albert Szent-Györgyi Medical University, Szeged. I lungary; '’Department of Dermatology, University of Erlangen-Nürnberg. Erlangen. FRO
Key Words. CD21 antigen • CR2 ■C3d receptor • Keratinocytes • Psoriasis • Skin diseases Abstract. Human keratinocytes are able to synthesize and express cell surface moieties characteristic of effector and/or accessory cells of the immune system (CD 16, CD36. HLA-DR. intercellular adhesion molecule-1). In the pres ent study, skin biopsies from healthy volunteers, from patients with psoriasis vulgaris (PV). mycosis fungoides (MF), purpura pigmentosa chronica (PPC), acute urticaria (AU) and from positive tuberculin skin tests were investigated with regard to the reactivity with the monoclonal antibodies to complement receptors CR 1CR2 and CR3 by means of a multistep immunoperoxidase method. In the clinically involved skin of all patients with PV. MF or PPC, and in biopsies obtained from positive tuberculin tests, specific epidermal intercellular staining with OKB7 and Leu anti-CR2 was seen on subcorneal keratinocytes. This finding suggests a differentiation-linked expression of CR2 on human keratinocytes in cytokine-mediated skin diseases whereas CR1 and CR3 arc apparently not expressed.
body Leu-1 lb (CD16), which is a typical marker of NK cells and granulocytes [6], and under certain circum stances (in different cytokine-mediated dermatoses such as mycosis fungoides (MF). psoriasis vulgaris (PV). purpura pigmentosa chronica (PPC), and in positive tu berculin skin tests, etc.) they also become HLA-DR-, HLA-DQ-, CD36- and intercellular adhesion molecule-1 (ICAM-l)-positivc [7, 8], To get further information on the surface character istics of HK, we investigated the expression of CR1, CR2 andCR3 in the epidermis of healthy volunteers and in that of patients with different dermatoses. The present study provides evidence that in the skin of patients with PV, MF or PPC and in biopsies obtained from positive tuberculin skin tests HK of the subcorneal cell layers specifically react with the monoclonal antibodies OKB7 (CD21) and Leu anti-CR2 (CD21). but not with those against CRI and CR3.
Materials and Methods Patients Investigations were carried out on surgical skin specimens from 10 healthy volunteers who underwent plastic-surgery, and on punch biopsy specimens (3 mm) of involved and uninvolved skin from patients with
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/7/2018 4:31:47 PM
Different cell types of the immune system possess spe cific receptors for complement fragments (CR). The bestcharacterized receptors for complement components arc those for the major split fragments of C3. CR1 (C3b receptor; CD35) is expressed on the surface of myeloid cells and has three major physiological functions: it is a cofactor for enzyme factor I in the cleavage of C3b to iC3b; it represents a receptor mediating endocytosis and phagocytosis of opsonized particles; and it participates in eliminating immune complexes and other cell particles bearingC3 and C4from the circulation [ 11. CR2 (CD21) is a receptor located on B lymphocytes, dendritic cells and nasopharyngeal epithelial cells [2—4]. Its ligands are C3d and the Epstein-Barr virus [5], The induction of B cell memory and of an efficient secondary response are pre sumed to be mediated through CR2 [ 1]. CR3 (CD 1lb) is a receptor for iC3b and for certain carbohydrate residues present on zymosan and beta-glucan particles. This recep tor is restricted to cells of the myeloid series and to natural killer (NK) cells. Ligation of this receptor may induce phagocytosis [1, 3). It is well known that human keratinocytes (HK) are able to express cell surface antigens characteristic of effector and/or accessory cells of the immune system. Thus, they specifically react with the monoclonal anti
CR2 Receptor on Subcorneal Kératinocytes
185
Fig. 1. CD21 expression on subcorneal human kératinocytes in involved psoriatic skin (a) and in tuberculin-positive skin (b). A EC X 400.
Immimohistochemistry 4-[im sections were cut on a cryostat and reactivity with monoclonal antibodies Leu anti-C R l. Leu anti-CR2. OKB7 and OKMI (table 1) was visualized by means of a multistep immunoperoxidase method described by Poppema et al. [9], Briefly, cryostat sections were frozen at -70 °C for at least 24—18 h. A fter thawing, they were immediately washed in phosphate-buffered saline (PBS). pH 7.2. and incubated with the monoclonal antibodies for 30 min at room temperature. The sections were subsequently washed 3 times in PBS and incubated with peroxidase-conjugated rabbit-antimouse antibody (Dakopatts. Glostrup. Denmark) diluted 1:10 with human AB serum diluted 1:1 with PBS (SPBS). This was followed by PBS washing and by a 30-min incu bation with peroxidase-conjugated swine-antirabbit antibody (D ako patts) diluted 1:10 with SPBS: After 3 w'ashcs with PBS. the specific peroxidase activity was revealed by usingaminoethyl carbazoie (A EC) as substrate, followed by a 10-min rinse in distilled water. Finally, counterstaining was performed with hemalum. Two kinds of negative con trols were included: firstly, omission of the primary monoclonal anti body and. secondly, substitution of the primary antibody with irrele vant antibodies (mouse monoclonal antibodies IgG, and IgG.a: Bccton Dickinson).
Results There was no specific positive staining as concerns CD35 (C R I) and CD 11b (CR3) expression on epidermal
Table 1. Murine monoclonal antibodies directed against human cell surface markers Antibody
CD
Protein content, ug/ml
Leu anti-C R l1 Leu anti-CR2‘ OKB72 O KM I2
CD35 CD21 CD21 CD 11b
6.25 1 10 2
1 2
CD = Cluster designation. Becton Dickinson. Mountain View', Calif.. USA. Ortho Diagnostics. Raritan. N.J.. USA.
cells (neither HK nor Langerhanscells) in specimens from the investigated persons, but in all skin biopsies from posi tive tuberculin reactions, from patients with PV, MF or PPC the dermal inflammatory infiltrate exhibited CD1 lb (CR3)- and CD35 (CR1 )-positive cells. On the other hand, in all biopsies from positive tuber culin reactions and from patients with PV, MF or PPC HK of the subcorneal cell layers exhibited a net-like specific positive staining when exposed to Leu anti-CR2 (CD21) (fig. 1) or OKB7 (CD21). No specific CD21-positive staining of FIK was observed in skin specimens of healthy volunteers, in those of patients with AU and in the clin ically uninvolved skin of patients with PV. MF. or PPC. In 4 of the 10 patients with PV, typical Munro abscesses containing CD35 (CR1)- and CD1 lb (CR3)positive leukocytes were revealed.
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/7/2018 4:31:47 PM
PV (n = 1()). MF stage II (n = 3). PPC (n = 3). acute urticaria (Au: n = 3) and on biopsies obtained from positive tuberculin skin tests (72 h after injection of purified protein derivate: n = 3 ). None of the patients had been involved in any systemic treatm ent or had used topical corti costeroids during the last 3 weeks before the biopsy. Each specimen was immediately frozen in liquid nitrogen.
■a
186
Hunyacli/Simon/Ketuleressy/Dobozy
The surface characteristics of different cell lines (such as T and B lymphocytes, monocytes/macrophages, etc.) constantly change during their differen tiation. Similarly, the expression of the surface moieties on I IK also reflects their stage of differentiation. Thus, the expression of CD 16 is detectable on the surface of basal HK in normal skin. In delayed-type hypersensi tivity reactions, the same antigen also appears on the surface of subcorneal HK. while cells of the stratum spinosum often remain negative or give only a weak positive intercellular reaction with the Leu-1 lb anti body. The intraepiderm al expression of CD36 in both delayed-type hypersensitivity reactions and in lichen planus is very similar to that of CD lb under the same clinical conditions [6, 7|. CR2 is a receptor located on B lymphocytes and den dritic cells (absent from CD 1-positive Langcrhans cells) |2. 3). Evidence of anti-CR2 reactivity of nasopharyngeal epithelial cells also exists [4|. C3d (35 kD). a degradation product of the third component of the complement, is the ligandof CR2. Several studies indicate that, in addition to C3d. CR2 also binds iC3b, C3dg and Epstein-Barr virus [5. 10]. CR2 enables B lymphocytes in areas distant from sites of inflammation to bind fragments of C3 in conjunc tion with immune complexes or bacterial particles. The induction of B cell memory and of efficient secondary responses is presumed to be mediated by this receptor [ 11]. The present study yields evidence that in biopsies obtained from tuberculin-positive skin and in those from the involved skin of patients with PV. M For PPC subcor neal HK specifically react with anti-CR2 monoclonal anti bodies. In contrast, the uninvolved skin of patients with PV. MF or PPC. both the involved and uninvolved skin of patients with AU. and skin specimens of healthy volun teers failed to display CD21 antigen. These findings sug gest that in a certain stage of differentiation HK. like human pharyngeal epithelial cells [4] and human B lymphocytes ¡12], may express CR2. The absence of CD21 antigen on subcorneal HK in skin specimens obtained from patients with acute urticaria suggests that CD21 expression of subcorneal HK might be con nected with cytokine-mediated skin reactions. Whether the acquired, presumedly not disease-specific, antiCD21 (CR2) reactivity of lesional HK in cytokine-medi ated skin diseases is due to C'R2 synthesis by HK. and whether it fulfils an immune function, remains to be eluci dated.
Acknowledgements The excellent tcehnical assistance of Miss W. Leisgang and Miss B. I iusslcin is gratefully acknowledged. This work was supported by grant Si 291/4-1 from the Deutsche Forsehungsgemei nscha ft.
References 1 Walport MJ. Lachmann PJ: Allergy, immune complexes and the complement cascade: in Lessof M il. Lee T H . Kemeny DM (eds): Allergy: An International Textbook. Chichester. Wiley. 1987. pp 217-236. 2 Weis JJ. Fearon DT. Kiekstein I.B. Wong WW. Richards SA. De Bruyn Kops A. Smith JA . Weis J 11. identification of a partial cDNA clone for the C3d/Epstein-Barr virus receptor of human B lymphocytes: Homology with the receptor for fragments C3b and C4b of the third and fourth components of complement. Proc Natl Acad Sei USA 1986:83:5639-5643. 3 Ross G D . Medof ME: Membrane complement receptors specific for bound fragments of C3. Adv Immunol 1985:37:217-267. 4 Young LS. Clark D. Sixbey JW. Rickinson AB: Epstein-Barr virus receptors on human pharyngeal epithelia. Lancet 19864:240-242. 5 Fingeroth JD . Weis JJ. Tedder TF. Stromingcr JL. Biro PA. Fea ron DT: Epstein-Barr virus receptor ofhum an B lymphocytes is the C3d receptor CR2. Proc Natl Acad Sci USA 1984:81:4510-4514. 6 Simon M Jr. Hunyadi J: Leu-1 lb (CD16) antigen expression on human kératinocytes. Arch Dermatol Res 1988:280:176-178. 7 Hunyadi J. Simon M Jr. Dobozy A: Immunologischc Bedeutung humancr Keratinocyten. Zcntralbl Haut 1990:157:673-685. 8 Simon M Jr. I leese A. Gôtz A: lmmunopathological investigations in purpura pigmentosa chronica. Acta Derm Venereol (Stockh) 1989:69:101-104. 9 Poppema S. Balm AK. Reinherz EL: Distribution of T-cell subsets in human lymph nodes. J Exp Med 1981:153:30-41. 10 R ossG D . LambrisJD: Identification of a C3bi-specific membrane complement receptor that is expressed on lymphocytes, mono cytes. neutrophils and erythrocytes. J Exp Med 1982:155:96-110. 11 Weis JJ.T oothaker LE. Smith J A. W cisJH . Fearon DT: Structure of the human B lymphocyte receptor for C3d and the Epstein-Barr virus and relatedness to other members of the family of C3/C4 bind ing proteins. J Exp Med 1988:167:1047-1066. 12 Tedder TF. Clement LT. Cooper MD: Expression of C3d receptors during human B cell differentiation: Immunofluorescence analysis with the I IB-5 monoclonal antibody. J Immmunol 1984:133: 678-683.
Received: June 18. 1990 Accepted: February 15. 1991 Dr. Janos I lunyadi Department of Dermatology Albert Szent-Gyorgyi Medical University, Szeged PO. Box 480 Szeged (Hungary)
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/7/2018 4:31:47 PM
Discussion
