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balance between helper and suppressor T cells is tilted toward helper activation. At the Congress, the workshop presentations reflected the increasing recognition of the importance of T cells in regulating disease progression. Several groups had examined the target organ to assess the subset composition of the cellular infiltrate, as well as (or instead of) the peripheral blood. G. Canonica (Genova) reported the presence ofIa + T cells and a subset (5/9 +) of OKT4 + cells in thyroids of patients with Hashimoto's disease, which proliferated in response to human Tg. This observation extends recent work showing that the thyroids contained a higher proportion of 5/9 + helper T cells and more B cells than did peripheral blood lymphocytes. Y. Kong (Detroit) discussed the kinetics of T-cell infiltration into the thyroids of mice as EAT develops. These mice harbor Lyt 2 + cells cytotoxic for thyroid monolayers. In contrast to the peripheral blood, there was an early dominance of Lyt 1÷ cells in the thyroid, followed by a relative increase in Lyt 2 + cells which shifted the Lyt 2+/1 + ratio from about 7 to 2. While B cells remained below 5%, the total number of T cells in the thyroid gradually decreased and were replaced by non-T/non-B cells. Clearly, T-cell subsets in end-organs do not correlate with those in the blood and analysis of

blood alone has contributed to past conflict in the data on immune status derived from patients with autoimmune thyroid disease. It was thus encouraging to note several attempts to analyse lymphocyte subsets at the site of involvement, including the lung in interstitial lung disease (G. Cordier, Lyon) and sarcoidosis (,J. Ceuppens, Leuven), the liver in chronic active hepatitis and the parotid in Sj6gren's syndrome (I. Frazer, Victoria). In the salivary infiltrate in Sj6gren's syndrome, R. Fox (La Jolla) noted higher numbers o f I a + and OKT10 + cells than in the blood and the presence of a B-cell subset not found in the blood. In the synovial fluid of rheumatoid arthritis patients, the proportions of O K T 8 ÷ and Ia ÷ cells were higher than in blood (J. Peterson, Copenhagen). At a summer conference on autoimmunity held two weeks before the Congress in Vermont, H. Wekerle (Wiirzburg) showed that T cells from myelin basic protein-propagated lines had infiltrated the brain lesion of rats with experimental autoimmune ehcephalitis and, interestingly, that the cells were adjacent to the vascular stroma that stained Ia + . The role Ia antigens may play at the target organ itself remains to be elucidated. Their role in promoting suppression when given with the immunizing

autoantigen did receive further attention at the Congress. Extending reported work, L. Steinman and M. Waldor (Stanford) described the administration of anti-I-A antibodies to mice immunized with mouse spinal cord or acetylcholine receptor in adjuvant. The incidence of experimental allergic encephalomyelitis and myasthenia gravis was each reduced. Suppression of myasthenia was transferable with splenic T cells. Similarly, N. Adelman (Stanford) and C. David (Rochester, MN) reported the suppression by anti-I-A antibodies in NZB/NZW Fi mice of the lupus-like syndrome and collagen-induced arthritis, respectively. It is as yet unclear if anti-I-A antibodies given in conjunction with autoantigen promotes antigen-specific suppression. Nor is the determination of T-cell subsets in target organs adequate without functional analysis, especially since cytotoxic and suppressor T cells may have the same phenotype. The answers to some of the currently vexing questions are likely to emerge in the next 3 years.

E M. Kong is in theDepartmentoflmmunology and Microbiology, Wayne State University School of Medicine, Detroit, M148201, USA.

Immediate hypersensitivity

Insights into mast-cell biology and IgE production from Mark Fletcher and Eric Gershwin

The 5th International Congress of Immunology was a forum for the presentation of considerable recent data on both disorders of, and the regulation of, immediate-hypersensitivity reactions. The program included a symposium on the mechanisms of both enhancement and suppression of IgE production as well as workshops on eosinophils; regulation of the IgE response; mast cells, basophils and triggering antigens; and mediators of immediatehypersensitivity reactions. In a major symposium devoted to enhancement and suppression of IgE production K. Ishizaka (Baltimore) described isotype-specific regulation of the IgE response, including the characteristics of an IgE-potentiating factor and an IgE-suppressive factor. Both bind IgE, are produced by T cells and have molecular weights of approximately 13 000-15 000 but they differ in carbohydrate content. The IgE-potentiating factor is positive for lectin binding; the IgE-suppressive factor is

negative. They appear to regulate IgE production by binding to IgE-forming B cells. Both are produced by the same T-cell line (W3235), so elaboration of either enhancer or suppressor activity is dependent upon the cells' environment. Factors that increase the glycosylation of proteins produce IgE-enhancing activity and factors that inhibit glycosylation lead to production of IgE-binding factors with suppressive activity. A factor which enhances glycosylation has a glycoprotein structure and kallikrein-like enzymatic activity. D. Katz (La Jolla) discussed similar ideas and indicated that the IgE antibody response was regulated via a very complicated and finely regulated system involving soluble factors. Two such factors he termed 'suppressive factor of allergy' (SFA) and 'enhancing factor of allergy' (EFA). SFA and E F A ' are neither antibodies nor M H C antigens, and unlike K. Ishizaka's factors do not bind IgE. SFA selectively inhibits an in-vitro IgE response system involving pokeweed mitogen-stimulated peripher-

al blood mononuclear cells; its effects are dependent upon the presence of Fc + B cells and Lyt- 1÷ T cells. The early results of collaborative efforts by D. Katz and K. Ishizaka indicate that SFA and EFA may be important in modulating the production of an IgE-induced regulator (EIR) which is very similar in properties to K. Ishizaka's IgE-potentiating factor. Further work will be needed to clarify the interrelationship and regulatory function of EFA, SFA and the potentiating and suppressing IgE-binding factors. Discussing another aspect of IgE regulation, A. Sehon (Winnipeg) presented data demonstrating the ability of antigens conjugated to modified polyethylene glycol (PEG) to suppress the IgE response to subsequent antigenic challenge. Dinitrophenyl (DNP) was coupled to monomethoxy-PEG (MPEG -DNP) to produce an antigen which, because most antigenic sites were masked, had low immunogenicity and allergenicity. Multiple injections of M P E G - D N P after initial sensititization

306 with DNP-ovalbumin in adjuvant led to suppression of IgE production and was felt to be due to increased suppressor: T-cell activity, increased IgG production and a decrease in affinity of the IgE produced. The subunit structure of the mast-cell IgE receptor has been elucidated by a carefully controlled solubilization procedure incorporating lipids into all steps to provide improved stability after the receptor purification (H. Metzger, Bethesda). H. Metzger proposed that the receptor was a glycoprotein containing three subunits: a, available to the extraceUular environment; /3; and a newly discovered ), component which is felt to be linked to the/3 component, both of which reside in the portion of the receptor which is embedded in the plasma membrane, and might protrude into the intracellular environment. T. Ishizaka (Baltimore) presented data elucidating the triggering mechanisms of IgE-mediated mast-cell mediator release and compared the responses of isolated human lung mast cells and a recently isolated line of cultured human basophils. The selective culture of human basophils from umbilical-cord blood mononuclear leukocytes was achieved by incubation of the cells with interleukin-2-supplemented supernatants of phytohemagglinin (PHA)stimulated T-cell cultures. The resultant cultured cells appeared by ultrastructure to be human basophils, were OKT3negative, contained histamine and had 3.83 x 105 IgE receptors per cell (Km = 2.75 x I0 9 M). T. Ishizaka found that within seconds oflgE-receptor bridging, a maximal increase in cAMP and [3H]methyl incorporation into phospholipids was seen, followed by a slower increase of intracellular Ca 2+ and release of histamine. The cultured basophils and lung mast cells showed identical biochemical and kinetic responses to IgE-receptor cross-linking by either DNP-anti-DNP IgE or anti-IgE. A model for IgEreceptor-bridged mast-cell activation was proposed in which the activation of a membrane-associated protease is associated with a rapid rise in cAMP and lipid transmethylation followed by Ca 2+ influx and mediator release. F. Austen (Boston) presented data on the chemistry and function of mast-cell granules and described the considerable heterogeneity of content, function and membrane-derived lipids when comparisons were made between human lung mast cells, rat peritoneal mast cells and a murine T-cell-dependent cultured mast-cell line. Mast cells are a valuable source of neutral proteases but the specific composition of proteases varies con-

Immunology Today, vol. 4, No. 11, 1983

siderably between mast-cell types; rat peritoneal mast cells are rich in carboxypeptidase-A and chymotrypsin while human lung mast cells have none. In murine T-cell-dependent mast cells, which may be grown from hemopoietic tissue using interleukin 3, chondroitin sulfate is the predominant peptidoglycan while in rat peritoneal mast cells it is heparin. In addition, mast cells vary in the metabolites of arachidonic acid which are produced; human lung mast cells and peritoneal rat mast cells generate predominantly prostaglandins, while the T-cell-dependent murine mast cells produce leukotrienes (especially LTB4). The workshop on eosinophils focused on the regulatory mechanisms of eosinophil accumulation in inflammatory lesions on a histological, biochemical and biological level, and included discussion of factors affecting tissue accumulation ofeosinophils, generation and characterization of eosinophil chemotactic factors, and functional aspects of eosinophil physiology. In addition, a few papers provided data on eosinophil cationic proteins (ECP), and used monoclonal antibodies to ECP to demonstrate heterogeneity of isolated eosinophils. Indirect evidence was provided for the role of eosinophil cationic protein in the fibrosis seen in patients with the hypereosinophilic syndrome. The workshop on the regulation of the IgE response focused mainly on the presence of T-cell subsets and T-cellderived factors that regulate specific IgE production. In the rat a factor derived from pertusssis-stimulated normal T cells was found by M. Iwata et al. (Baltimore) to enhance the glycosylation of IgE-binding factors during their biosynthesis. The factor had a kallikreinlike enzymatic activity and was felt to be important in the selective formation of IgE-potentiating factor. A suppressive factor of molecular weight 15 000 was described by T. Ueda etal. (Baltimore) in the rat system which selectively suppressed IgE production by mouse plasma cells and the expression of surface IgE on B cells. In the workshop on mast cells, basophils and triggering antigens A. Dvorak (Boston) gave a brief summary of the morphological features which distinguish mast cells from basophils: basophils demonstrated irregularly placed blunt cytoplasmic processes, a segmented nucleus and large granules, while the mast cell had elongated regularly spaced pseudopods, a singie-walled nucleus and smaller, irregular but more numerous granules than the basophil. A number of papers described the condi-

tions necessary for the production and maintenance of mouse mast cell and human basophil-like cell cultures which usually required the presence of T-cellderived products and/or fibroblasts or fibmblast-derived factors. A group of papers presented data on the characterization of specific allergens in the hope that the techniques may help to standardize common antigens such as house dust mite or pollen as well as characterize their structure-function relationships. The workshop on mediators and mechanisms of immediate-hypersensitivity reactions focused on two areas, the production, metabolism and function of • leukotrienes (LTs) and the role ofIgG 4in atopic disease. W. K o n i g e t a l . (Bochum, FRG) localized the neutmphil enzyme systems felt to be important in the production of5-HETE, LTC~ and LTB4 to the high-speed supernate and pellet (200000 g) of fractionated human polymorphs. W. Henderson and S. Klebanoff (Seattle) presented evidence indicating that L T C 4 is degraded by normal polymorphs via the myeloperoxidase-H202-halide system, by O H . (hydroxylradical) in patients with myeloperoxidase (MPO) deficiency and not at all by cells from patients with chronic granulomatous disease. They conclude that LT production does not require a respiratory burst but that destruction of LTs via the MPO-H202-halide system may be an important mechanism by which normal polymorphonuclear neutrophil leukocytes limit LT activity and thus inflammation. Several papers presented data indicating that IgG 4 may have both enhancing and suppressing activity in atopic disease. T. Nakagawa et al. (Tokyo) demonstrated that IgG 4 increases after repeated antigen exposure in association with amelioration of clinical symptoms behavior consistent with the action of blocking antibodies. It was clear from both the number and quantity of papers presented that recent discoveries in the basic biology of both IgE production and mast-cell degranulation have major therapeutic implications. We suspect that the 6th International Congress in Toronto will focus on the use of T-cell factors and on antigen modification in selectively modulating clinical manifestations of allergic disease, at least in animal systems.

Mark P. Fletcher and M. Eric C,ershwin are in the Universi~ oafCalifornia at Davis School ofMedidne, Davis, CA 95616, USA.