Applied wisdom

Immunology Today June 1982

Transplantation

Receptors, antibodies and disease

Applied wisdom

from J o h n N e w s o m - D a v i s and A n g e l a V i n c e n t Biochemists, endocrinologists, immunologists and neurologists share an interest in cell surface receptors, as was cvidcnt at a recent symposium held by the Ciba Foundation*. When these receptors are targets [or at.ttoantibodies, endocrine or neurological disease can result. Attention focussed particularly on receptors (R) for thyroid stimulating hormone (TSH), insulin, acetylcholinc (ACh), prolactin and [32-adrenergic agonists. The clinical importance of autoantibodies to receptors, judged purely in nurnerical terms, varies considerably. Insulin-resistant diabetes (insulin-R antibody), for example, is extremely rare - less than 50 cases * Receptors Antibodies and Disease (Ciba Symposium no. 90) was organized by I)r David Evered and (:haired by Professor N. A. Mitchison. The proceedings will bc published by Pitman Medical Ltd.

have been reported worldwide, to date. ()n the other hand Graves' disease (TSI I-R antibody) and myasthenia gravis (ACh-R antibody) are moderately prevalenl while asthma and other atopic disorders ([3e-adrenergic-R antibody) are very common. Direct implication of the relevant antibodies in the disease process scems well established for most of the disorders discussed, although some uncertainty exists aboul lhe role of the recently identified [%-adrenergic-R antibody. In asthma a reduction in lung tissue ,ge adrenergic receptors, as measured by agonist binding or !3e responses, has been established for some time and antibodies specific [or the [32 receptor can be identified either by' inhibition of agonist binding, by immunoprecipitation of solubilized /70

2. Insulin-R

1. AChR

3. Prolactin -R

,.rllmm.d ,m p

4, 8 2- adrenergic- R

,5 TSH- R

Fig. 1. Diagrammatic representation (roughly to scale) of proposed subunit structures of the principal receptors discussed, indicating the size and number of binding site(s) for the natural ligand (hatched). P,eceptnrs are ranked (1-5) according to the information available. Numbers denote the rnol. wt.

from E l i z a b e t h S i m p s o n T h e t r a d i t i o n of a n a n n u a l " R o u n d T a b l e

Symposium on Applied Immunology' was carried into its 13th year in Axams, Austria, on 25-27 ,January. ()n these occasions small numbers of clinicians and scientists meet to discuss new developments in researcb that have mutual interest. In the opening session on cellsurface antigens H. Bather (Riisvijk) discussecl the itt-me', effect of monuclonal antibodies (MAbs) directed against '['-cell subsets in Rhesus monkeys grafted with alh)geneic skin. The MAbs defined human lymphocyte subsets that erossreaet with the equivalent rhesus monkey cells. Antibodies against tile helper/inducer subset (OKT4 equivalent) prohmged skin allograft survival whereas those directed against the cylotoxie/suppresser subset (()KT8 equivalent) not only failed to prolong surviwd but may have shortened it. These resuhs at'(" in line with recenl reports that in mite and rats the T cells involved in initiating graft rejection are of the helper (Lyl + ) phenotype and not the tyrotoxic/suppressor (l.yl+ ~ ) i~heno-. type. 1). Arndt-Jovin ((;6ttingen) presented her use of sophisticated physical methods (fluorescence energy transfer, rotational diffusion and translational diffusion) to assess the density, proximity and mobility of mouse• II-2 ( Kk) antigens delected with monoclonal antibodies. The basic information obtained fi'oni ll~ese studies should alloy, direct examination of how tt-2 antigens 'assoeiate' with such extrinsic antigens as viruses and thus tbe necessary eunsh'aints ful considering l l~c ahered self versus dual receptor hypothesis of T-ceil re¢et> tors. P. Peterson (Uppsala) ln'esentcd
Immunology Today, vol. 3, No. 6, 1982 Receptors, antibodies and disease - cong. antigen may be the principal factor underlying the post-operative decline of specific antibody in thyrotoxicosis and myasthenia. Several mechanisms that might trigger breakdown in tolerance to self antigens and lead to production of autoantibody were discussed, but there was a noticeable lack of firm data. Some features of the autoimmune response should provide clues here. First there is evidence of heterogeneity in the clinical expression of the disease. Myasthenia gravis, for" example, appears to exist in several forms as indicated by differences in thymus pathology, age of onset, antiAChR titres, and in its association with HLA antigens, and possibly with Gm allotypes. Secondly, as has long been recognized, certain autoimmune diseases tend to associate with each other. HLA antigens could contribute to this: HLA-A1, B8, DR3 occur at increased tYequency in Graves' disease, juvenile diabetes and myasthenia. Thirdly, the antibody response seems to be restricted in the number of antigenic sites to which it is directed. Thus, the spontaneously occurring antithyroglobulin antibody in man is made against only four epitopes (Ivan Roitt, Middlesex Hospital Medical School) in contrast to the response in Transplantation

c¢mtinued./}r*mp. 149

an analysis of the a and 13chain structure of class II (Ia) MHC antigens which suggested a much closer homology with class I M H C antigens (heavy chain plus [3-2 microglobulin) that has previously been considered likely. Such structural and sequence homologies probably reflect comparable functions - a view which now has many adherents (see Klein, J. e/a[., 1981 .JVature 291,455). The interaction of penicillin, an extrinsic antigen, wilh cell-surface determinants was analyzed by F. Claas (Leiden). Patients with druginduced thrombocytopenia have antibodies directed at epitope(s) on the interaction molecule formed on the surface of platelets by the drug plus a platelet antigen (not an MHC antigen in this case). High levels of penicillin ire vitro can interfere with typing lbr HLA (class 1 antigens) with conventional alloantibodies and Claas suggested that combinational associations of certain MHC antigens with penicillin could account for these

151 immunized rabbits in which the number of antigenic sites recognized is tenfold greater. The varying genetic influence on autoimmune disease can be studied in detail in NZB mice (John Knight, Otago University Medical School). Genetically identical mice of this strain differ in the age at which a particular autoimmune disease develops, and some animals escape it altogether. A small number of dominant genes appear to control this susceptibility. These genes can decrease or increase the relative risk of developing autoimmune disease and they are not confined to the MHC. Thus, the idea that a single gent is responsible for the development of a particular disorder, and that incomplete linkage disequilibrium accounts for the failure to observe high levels of association with a particular HLA antigen in individuals with a given autoimmune disease, appears to be under threat. As an alternative hypothesis it was proposed that histocompatibility antigens could predispose through somatic mutation to diversification of forbidden clones. For instance, the absence of a particular anti-idiotypic clone could lead to an increased number of self-reacting clones with shared idiotypes. Despite covering much of what is

known about the biochemistry and immunology of the various receptors, the meeting reached no conclusions concerning the aetiology of the specific diseases represented. One might ask for instance why in some conditions antibodies appear to be predominantly against a hormone agonist binding site, whereas in others they are not; or why the TSH-R is a relatively common target compared to t h e insulin-R; and whether there are any obvious aetiological differences between so-called 'organ' and 'nonorgan' specific autoimmune diseases. The meeting closed with a perspective by Melvin Blecher (Georgetown University School of Medicine) who proposed some diseases in which autoantibody specificities misht be defined when probes for the relevant receptor became available (e.g. parathyroid antibody in autoimmune hypoparathyroidism; pancreatic islet cell antibody in diabetes). The association of these diseases with others in which antireceptor antibodies have already been demonstrated would support this proposal.

John ,N}w.rom-Davir and Artgela [%cenl are in the De/)arlmet~! o[ .N}'uro/ogical Sczence, Royal Free Ito.~-/)ita[ School q/ Mediczne, Lor~do*~N W 3 2Q(;.

findings. Thus, the 'restriction' (by MHC and non-MHC cell surface determinants) of antibodies may be a widespread phenomenon, analogous to that of T-cell restriction. E. Simpson (London) discussed male-specific immune responses in karyotypically abnormal mice and concluded that the H-Y antigen seen by H-2 restricted cytotoxic T cells, which determines graft rq}ection, and the SDM antigen detected serologically were not the same - contrary to past assumption. The sex determining role of either is a question of debate. The session on fuTlction of antibodies i~z viva started with an elegant analysis of the three dimensional structure of myeloma protein crystals by R. fluber (Miinich). Within this session M. Horowitz (New York) compared the effect of specific antibody (with or without complement and in the presence of phagocytic cells) on Fscherichia coil and £
destroyed whereas L. pneamophila continues to grow intracellularly. Patients with Legionnaires' disease usually make antibodies to the organism hul recover only if they also mount a cellmediated response. Immunocompromised patients are most at risk of a fatal outcome. In the session on immunosuppressign, mostly in relation to transplantation, R. Calne (Cambridge) summarized his very encouraging results with cyclosporin A in kidney (vansplant patients, who can be maintained on the drug alone providing the dose can be kept below a nephrotoxic level a complication encountcrcd in the first clinical trials and which often prohibits the drug's use in hepatic transplant patients. Exl)el'imenlal findings with allogeneic liver transplants in rats match those reported earlier for pigs, namely that such grafts are tolerated withoutthe need for immunosuppression and precondition the recipient lo receive kidney and even skin grafts from an identical donor. This effect has been transferred o*ltimledonp. 1.52

Immunology Today, vo/. 3, Wo. 6, 1982

152 with serum fi'om liver gralted rats, but the functional molecule in such serum has not yet been identified. The problems of pancreatic grafting were discussed by R. Calne, W. Land (Miinich) and P. Morris (Oxford). Segmental pancreatic grafts with blocked exocrine function have becn given to diabetic patienls receiving kidney grafts. These patients have lost their own kidneys through diabetic ncphrosis. Such pancreatic grafts function for a period of weeks or' months but usually fail, in contrast to the kidney grafts in the same patients. Fibrosis of the engrafted pancreas, together with immunological rejection, seems to account for these rather disappointing results. P. Morris reported the results of experiments

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Interleukins: a rose is a rose... SIR:

As one of" the original signatories of the interleukin nomenclature system, proposed at the 2nd International Lymphokine Workshop 1 am forced to take objection with Dr Larsson's denunciation (Immunology Today, April 1982, 81) of the system as a 'Humpty Dumpty approach' to the naming of immunoregulatory proteins. Its purpose was to rid the literature of a bewildering plethora of acronyms and factors. The use of the term Interleukin was based fully on a consensus of opinion and hard biochemical data from a number of international laboratories which suggested that various lymphokine/monokine assays were actually not measuring 6-10 discrete activities but were clearly detecting the effects of only two immunoregulatory proteins (Interleukins 1 and 2). 1 feel, and I am certain that several of my colleagues would continue to agree, that an ILI / I L - 2 nomenclature is far less confusing than a lymphokine literature riddled with the likes of TAF, TSF, TMF, THF, KAF, LAF, TCCF, costimulator, etc. I can only agree with Dr Larsson's cry of anguish that in the current literature some investigators have haphazardly slapped the names of ILl and IL-2 on poorly defined activated

with rats in which isolated pancreatic islets were placed under the capsule of a syngeneic kidney, and the two components then together grafted as an allograft. The kidney seems to provide protection against rejection of the islet tissue, which continues to secrete insulin. The practical problems of isolating suflicient islet tissue tbr thc sort of manoeuvre in man, however, are somewhat daunting. R. Batchelor (London) discussed the retransplantation into parental slrain rats of F1 hybrid kidneys from rats of the parental strain induced to accept the grafts by enhancement. Such retransplanted kidneys devoid of FI 'passenger leucocytes' were generally accepted and rejection could not be induced by ir~jections of either B or T lympho-

cytcs of F1 hybrid origin into the second recipient. In contrast, injections of even very small re|tubers of F1 dendritic cells induced rejection, suggesting that this cell type is the prime antigen-presenting cell. This result is in line with recent results iri vilro. The combination of basic and applied science, on the evidence of this and previous meetings in thc series, stimulates ideas and discussion on both sides. Manipulation of the immune response to permit organ grafting has not been easy and many questions are yet unanswered, but the results obtained clinically and in various experimental systems have thrown light on many of the interacting humoral and cellular elements which regulate the immune response.

macrophage and T-cell supernates. Unfortunately, that is not the problem of nomenclature but is a direct result of the unwillingness of several researchers to approach lymphokines by using biochemically defined reagents whose effects can be monitored as activities on purified or cloned cell populations. Legitimate IL-I and IL-2 preparations clearly can perform under such rigorous standards, whereas acronyms of biochemically undefined differentiation inducing activities cannot. As an example of how the Interleukin nomenclature has played an important role in understanding previously complex areas of cellular interactions, a consensus appears to be emerging in current publications that IL-2 can act only to augment plaque-forming cell responses to purified B ceils when tested either in the presence of contaminating T cells or perhaps a second T-cell-derived lymphokine ~. I"urthermore, only by careful examination of the effects of purified IL-1 and IL-2 preparations on homogeneous cell populations have investigators been able to dissociate the effects of T-cell replacing factors (late acting B-cell differentiation inducing moieties) from a previously undiscovered B-cell growth factor 2, Furthermore, Dr Larsson's impatience with the conflicting properties ascribed to a hastily proffered IL-3 protein may be relatively short-lived in that several symposia speakers at the 1982 American Association of Immunologists Meeting in New Orleans, in April, revealed that IL-3

(as defined by its capacity to induce 20 Alpha steroid dehydrogenase in immature lymphoid cells) is simply type 2 colony stimulating factor. As an investigator who wishes to study the molecular organization of lymphokine function and regulation, I have far more patience tot awaiting the consensus of experimental evidence (such as will no doubt be produced at the 3rd International Lymphokine Workshop to be held this summer in Pennsylvania) to determine Interleukin nomenclature than I have for returning to the era where any multicellular assay in which crude mitogcn-containing supernates score positive, will by implication define a novel factor and another mindboggling acronymn. To pick up on Dr Larsson's nursery rhyme metaphor, if indeed lymphokine investigators wish to cause the ttumpty Dumpty Interleukin to 'have a great fail' then I am afraid that 'all the king's post-docs and scientist's men (sic) will be hardpressed to put lymphokines back together again.' STEVEN GUJJS

Program in Ba.de lmmurtology, Fred Hulehinson Cancer Re.search Cenler, Sea/l/e, Washinglon 9870d, U.S.A.

References 1 Swain, S., I)ennert, G., Warner, J. and Dutton, R. (1981) 15oc. Nat/ Acad. Sci. U.S.A. 78, 2517 2 Howard M., Farrar, J., I[ilfiker, M., Johnson, B., Takatsu, K., Hamaoka, T. and Paul, W. E. (1982)J. Exp. Med. 155,914