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Insulin dependent diabetes mellitus, an autoimmune disorder?
CLINICAL
IMMUNOLOGY
AND
Insulin
IMMlINOPATHOLOGY
53. sY?-s% (1989)
Dependent Diabetes Mellitus, Autoimmune Disorder?’
an
WILLIAM J. RILEY Department
of Pathology,
University
qf Florida,
Gainesville,
Florida
32610
During the last 25 years the concept of a chronic autoimmune process leading to the development of insulin dependent diabetes (IDD) has emerged. The presence of two animal models for IDD, the BB rat and the NOD mouse, has improved our ability to understand the process leading to p cell destruction. The hallmark of an autoimmune disease is the characteristic pathologic lesion of mononuclear infiltration of the pancreatic islets. Further histologic studies of the diabetic pancreas have identified the type of cells infiltrating the islets and led to the concept of pancreatic p cells capable of presenting antigen. The initial description of linkage disequilibrium of HLA DR3 and DR4 alleles with IDD has now progressed to the molecular level with the identification of residue 57 of the HLA DQ p chain as crucial to the genetic predisposition to IDD. Autoantibodies to cytoplasmic antigens (ICA), surface antigens, or a membrane protein of 64 kDa identified by immunoprecipitation, autoantibodies to secreted products such as insulin and proinsulin, and autoantibodies that are cytotoxic to cultured p cells are islet specific autoantibodies that have been described. Some are probably only markers of immunologic activity; others might participate in the destruction itself. The use of ICA as a screening tool has been successful in identifying individuals prior to the onset of IDD. Widespread cellular immunological defects have been identified both in animal models and in man. In the BB rat, a seeming paradox of severe immunodeficiency occurs in an animal with autoaggressive destruction of p cells. More subtle defects in immunoregulation have been described in the NOD mouse and in human IDD. The response of IDD in both animal models and in man to immunomodulation and to immunosuppression offers further evidence of an immunologically mediated disease. However, some therapies in the animal models, not typically considered immunologic, such as protein restriction and insulin therapy, have prevented IDD. The possibility of intervening prior to the onset of clinical disease at the level either of the initial process of recognition of the pancreatic p cell as a target organ or of the effector mechanism is approaching a reality in human IDD. “i 1989 Academic PXS, IIIC.
Insulin dependent diabetes mellitus (IDD) is one of the most common chronic illnesses in childhood. Effective therapy of IDD demands a lifelong commitment to daily multiple insulin injections and blood glucose determinations, as well as dietary and exercise constraints. Such therapy is not curative but is aimed at maintaining normoglycemia. Nevertheless, the morbidity and mortality remain high and life expectancy is shortened. Any approach to a cure or prevention of IDD will need to be directed against the underlying pathologic process (1). The onset of clinical disease represents the end stage or result of a chronic ’ Supported by a grant from the National Institutes of Health (AM36151) and a Clinical Research Center grant (RR 0082). Dr. Riley is the recipient of an NIH Research Career Development Award (AM01421). Presented as part of a symposium entitled “Autoimmunity and Immunointervention,” March 5-8, 1989, Scottsdale, AZ. S92 0090-1229/89 $1.50 Copyright 0 1989 by Academic Press, Inc. All rights of reproduction in any form reserved
IDD: AUTOIMMUNE
s93
DISORDER?
autoimmune destruction of the insulin-producing pancreatic l3 cells. Several features characterize IDD as an autoimmune disease: mononuclear infiltration of the pancreatic islets (insulitis) (2-5), association with the immune response genes of the major histocompatibility complex on chromosome 6, presence of a number of islet specific autoantibodies (1,6), defects in cell-mediated immunity (7), response to immunotherapy (8), and the frequent occurrence of other autoimmune diseases in affected individuals or in their family members (9). The natural history of the latent or presymptomatic phase of IDD (1) can be summarized briefly. In a genetically predisposed individual, an immunologically mediated destruction of the p cells gradually results in l3 cell elimination, loss of insulin secretion, and the onset of clinical disease. The ongoing immunologic process that is characteristic for the “prediabetic” phase can be identified by the presence of autoantibodies to a cytoplasmic antigen (ICA), to an immunoprecipitable protein of approximately 64 kDa (64KA), and to native insulin (IAA) (1, 6, 10). l3 cell function can be evaluated by determining the insulin response to glucose in an intravenous glucose tolerance test and oral glucose test (Table 1). There are still major gaps in our understanding of this autoimmune process. Initially, IDD was found to be associated with HLA B8 and B15. However, the linkage was later shown to be with HLA DR3 and DR4. Nearly 95% of IDD patients have a DR3 and/or DR4 allele, with 40% being DR3/4 heterozygotes. The DR4 association could be further subdivided by RFLP of genes of the DQP chain (DQw3) into a protective form, DQw3.1, and a susceptible form, DQw3.2 (3-5). Most recently the presence of a noncharged amino acid at position 57 of the DQp chain has been shown to be associated with IDD (4), while aspartic acid at that position was neutral or negatively associated with IDD. More than 90% of Caucasian patients with IDD possessed no alleles with a DQl3 aspartic acid at position 57 (4). Thus, the antigen binding affinity might possibly be influenced by the charge of the amino acid at this critical position. In conflict with this hypothesis is the observation that alleles from Chinese IDD patients were not associated with nonaspartic acid at DQP position 57. Alternatively. these particular HLA associations may be important in the regulation of the immune system. We recently described the increased relative antigen density of DR on the surface of T lymphocytes in patients who were HLA DR3/DR4 heterozygotes (7). The ability to identify future IDD patients months to years before onset of the disease by the detection of islet cell autoantibodies has documented the chronicity of the latent phase of this disease (1). Autoantibodies to cytoplasmic antigens of TABLE POSSIBLE
EXPLANATIONS
FOR
1 HLA ASSOCIATION
IN
IDD
1. Linked marker to the “diabetes gene” 2. Structural variation in HLA molecules a. Immune response Differential antigen peptide binding Differential expression of specific T cells, “hole” in T cell repertoire b. Molecular mimicry 3. Regulatory variation in expression of HLA molecules
s94
WILI.IAM
.J. RI1.F.k
all cells in the islet (ICA) and to insulin have been most widely used to detect prediabetes ( 1). In our studies, the presence of ICA detected before the age of 10 years in relatives of IDD patients was found to have an actuarial estimate of probability of developing IDD close to 100% after 5 years. Another significant factor in the prediction of IDD was the titer of ICA. The higher the titer, the higher the risk for developing IDD. However, ICA are reactive to an antigen(s) common to all islet cells, not only to the fi cells. Thus, neither ICA nor IAA are likely candidates for a role in the destruction of the p cells or for being the primary antigen. In our experience, IAA appear to reflect more active disease (6). The presence of ICA and IAA was associated more frequently with impaired insulin responses to an intravenous glucose infusion than the presence of ICA alone (6). The insulin responses to iv glucose and the concentration of IAA have been combined in a linear model to predict the time to onset of IDD ( 1I). In the rat, autoantibodies to a surface antigen(s) have been shown to have p cell specificity and thus might participate in the disease process (12). Recently, 64KA have been documented in the prediabetic phase of man and in both animal models of IDD, the NOD mouse and the BB rat (10, 13, 14). In a comparison of the three autoantibodies, ICA, 64KA, and IAA, 64KA were present in 20 of 23 sera from individuals who subsequently developed IDD, whereas ICA were found in 17 of 23 and IAA in I 1 of 23 (15). The ubiquitous and conserved nature of this antigen across species, the membrane and possibly surface nature of this protein, and the detection of 64KA before other islet specific autoantibodies offer plausible arguments for a primary antigen. Not only has the antigen (5) been elusive, but the mechanisms by which the pancreatic p cells are specifically recognized by the immune system and subsequently destroyed are also unknown. In an interesting study using transgenic expression of the SV40 gene in the pancreas of mice, the delayed expression of the SV40 antigen resulted in the lack of tolerance to this antigen (16). This delayed expression of an antigen might contribute to the pathogenesis. Immunohistochemical staining of human pancreases from newly diagnosed IDD patients has demonstrated aberrant expression of class I and class II antigens on p cells. Thus one could hypothesize that after an environmental trigger such as a viral infection and consequent induction of class II antigens, the /3 cells will be capable of presenting their own antigens in an immune response (17). In addition, we have confirmed the study of Gotfredsen et al. (18) in the BB rat and successfully used insulin therapy prior to the onset of IDD in the NOD mouse to prevent IDD, presumably by decreasing /3 cell activity and down-regulating the p cell antigen or by a direct effect of insulin on the immune system. One of the seeming paradoxes of autoimmune diseases is the development of an “anti-self’ process in individuals with primary immune deficiency disorders. Nowhere is this so apparent as in the BB rat. These animals have severely deficient numbers and function of T cells. They are unable to reject skin grafts and respond poorly in an allogeneic MLR or to mitogens (19). Also, they display marked lymphopenia with an inverted CD4 to CD8 ratio and lack the subset of cells defined as RT6 (19). Yet the p cells are destroyed. In man and the NOD mouse, the defects appear to be more subtle in comparison. Suppressor cell function is
IDD: AUTOIMMUNE
s95
DISORDER?
depressed and the T lymphocytes from NOD mice do not produce IL-1 to the same degree as other mice (20). We have recently found both a decreased number and function of the CD4 + CD45R - T cell population reflected by a defect in the ability of T cells to provide help in a pokeweed mitogen-driven T-B coculture assay in ICA+ prediabetic individuals. In addition, lymphocytes from these individuals produce less interferon-y than controls in response to mitogenic stimulation. How these defects relate to the final effector mechanism and how p cell destruction can be prevented remain to be determined. Table 2 summarizes many of
TABLE Agent or procedure (Ref. )
IDD model
2 Result
Silica (21, 22)
BB rats
Marked reduction of IDD
Insulin therapy (18)
BB rats NOD mice NOD mice BB rats NOD mice
Prevention of IDD
Protein-restricted diet (23) Streptococcal Prep. OK-432 (24) LCM virus (25, 26)
Mab to NK cells (28)
NOD mice BB rats BB rats
Reduces frequency of IDD Prevention of IDD and insulitis Complete prevention of IDD and insulitis Prevention of insulitis Prevention of IDD
I-E transgenic (29) Neonatal thymectomy (30)
NOD mice BB rats NOD mice
No insulitis Reduces frequency of IDD
Total lymphoid irradiation (3 I) Cyclosporins (32, 33)
BB rats NOD mice BB rats NOD mice
Lymphocyte transfusions (34-37) Allogeneic bone marrow transplantation (38, 39) Repeated phlebotomies (40)
BB rats
Reduces frequency of IDD Prevention and partial reversal of IDD Reduces frequency of IDD
Nicotinamide
Mab to CD4 (27, 28)
(40)
NOD mice BB rats
NOD mice BB rats
Prevention of IDD
BB rats
Prevention of IDD
NOD mice
Prevents IDD
Possible mechanism Macrophage inactivation or depletion Decreased p cell antigen expression 9 Increased CD8 cells? Decreased CD4 cells Elimination
of CD4
Elimination cells
of NK
‘3 Prevents cell-mediated immunity Immunosuppression Immunosuppression Reconstitution with normal immune cells Reconstitution with normal immune cells Stimulation immune removal positive
of system; of CD4 cells ?
S96
WILLIAM
J. RIl.F.1’
the prevention studies carried out in animal models. In man, no prevention trials have been done, although immunosuppression with steroids, azathioprine (Imuran, Burroughs-Wellcome Co.), cyclosporine (Sandimmune, Sandoz Pharmaceuticals Corp.), or immunotherapy using intravenous immunoglobulin or lymphocyte transfusions have been attempted in patients with newly diagnosed IDD (42). Immunosuppression has been shown to prolong the l3 cell function but complete remission has not been sustained for more than 3 years. In our studies using azathioprine and high dose steroid induction, we have demonstrated significant preservation of l3 cell function (8). A second remission was established with a second high dose methylprednisolone induction, albeit of limited duration, in one boy who remained in an insulin-free remission for 3 years. The major difficulty with treating patients at the onset of IDD is that this stage is the end point of the presymptomatic (latent) phase of the disease and very few l3 cells remain to be salvaged. Thus the approach to preventing the clinical expression of IDD needs to be done during the prolonged latent phase. As we understand the natural history and have improved our prognostic markers of the prediabetic state. prevention in man may now be possible. REFERENCES I. Riley, W. J., Winter, W. E., and Maclaren, N. K.. Identification of insulin-dependent diabetes mellitus before the onset of clinical symptoms. J Pediarr. 112, 314316, 1988. 2. Gepts, W., Islet morphology in type I diabetes. Behring Inst. Mitt. 123, 39-41, 1984. 3. Henson, V., Maclaren. N. K., Riley, W. J., and Wakeland, E. K., Polymorphisms of DQ beta genes in HLA-DR4 haplotypes from healthy and diabetic individuals. 1mmunogenetic.s 25, 152160. 1987. 4. Todd. J. A., Bell, J. I., and McDevitt, H. O., HLA-DQ beta gene contributes to susceptibility and resistance to insulin-dependent diabetes mellitus. Nature (London) 329, 599-604. 1987. 5. Nepom, B. S., Schwarz, D.. Palmer. J. P.. and Nepom, G. T.. HLA-DQ alpha- and beta-chains produce hybrid molecules in DR3/4 heterozygotes. Diubetes 36, 114-l 17, 1987. 6. Atkinson, M. A.. Maclaren, N. K., Riley, W. J., Winter, W. E.. Fisk, D. D., and Spillar, R. P., Are insulin autoantibodies markers for insulin-dependent diabetes mellitus‘! Diabetes 35,894-898, 1986. 7. Hitchcock, C. L.. Riley, W. J.. Alamo, A., Pyka, R.. and Maclaren. N. K.. Lymphocyte subsets and activation in prediabetes. Diabetes 35, 1416-1422, 1986. 8. Silverstein, J. H., Maclaren, N. K., Riley, W. J., Spillar, R., Radjenovic. D., and Johnson, S., Immunosuppression with azathioprine and prednisone in recent-onset insulin-dependent diabetes mellitus. N. Engl. J. Med. 319, 599-604, 1988. 9. Maclaren, N. K., and Riley, W. J., Thyroid gastric and adrenal autoimmunities associated with insulin dependent diabetes mellitus. Diabetes Cure 8, 34-38, 1985. 10. Baekkeskov, S., Landin. M., Kristensen. J. K., Srikanta, S., Bruining, G. J., Mandrup Pot&en, T., de Beaufort, C., Soeldner, J. S., Eisenbarth, G. S.. and Lindgren, F., Antibodies to a 64,000 Mr human islet cell antigen precede the clinical onset of insulin-dependent diabetes. J. C/in. Invest.
79, 926-934,
1987.
11. Maclaren. N. K., Rossini, A. A.. and Eisenbarth, G. S., International research symposium on immunology of diabetes. Diabetes 37, 662-665, 1988. 12. Pipeleers, D., Winkel, M., Dyrberg, T., and Lemmark. A., Spontaneously diabetic BB rats have age-dependent islet beta-cell-specific surface antibodies at clinical onset. Diabetes 36, 11 I I-1 1 IS, 1987. 13. Baekkeskov, S., Dyrberg, T., and Lernmark, A., Autoantibodies to a 64-kilodalton islet cell protein precede the onset of spontaneous diabetes in the BB rat. Science 224, 1348-1350. 1984.
IDD: AUTOIMMUNE
DISORDER?
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14. Atkinson, M. A., and Maclaren, N. K., Autoantibodies in nonobese diabetic mice immunoprecipitate 64,000-Mr islet antigen. Diabetes 37, 1587-1590, 1988. 15. Riley, W. J., Atkinson, M. A., Schatz, D. A., and Maclaren, N. K., Comparison of islet autoantibodies in “pre-diabetes” and recommendations for screening. J. Autoimmun., in press. 16. Teitelman, G., Alpert, S., and Hanahan, D., Proliferation, senescence, and neoplastic progression of beta cells in hyperplasic pancreatic islets. Cell 52, 97-105. 1988. 17. Pujol Borrell, R., Todd., I., Doshi, M.. Gray, D.. Feldmann, M., and Bottazzo, G. F., Differential expression and regulation of MHC products in the endocrine and exocrine cells of the human pancreas. Clin. Exp. Immunol. 65, 128-139, 1986. 18. Gotfredsen, C. F., Buschard, K., and Frandsen, E. K., Reduction of diabetes incidence in BB Wistar rats by prophylactic insulin treatment of diabetes-prone animals. Diabetologia 28,933-935. 1985. 19. Maclaren, N. K., Elder, M. E., Robbins, V. W.. and Riley, W. J., Autoimmune diatheses and T lymphocyte immunoincompetences in BB rats. Metabolism 32, 92-96, 1983. 20. Serreze, D. V., and Leiter, E. H., Defective activation of T suppressor cell function in nonobese diabetic mice: Potential relation to cytokine deficiencies. J. Zmmunol. 140, 3801-3807. 1988. 21. Charlton, B., Bacelj, A., and Mandel, T. E., Administration of silica particles or anti-Lytf antibody prevents beta-cell destruction in NOD mice given cyclophosphamide. Diabetes 37, 930-935. 1988. 22. Oschilewski, U., Kiesel, U.. and Kolb, H., Administration of silica prevents diabetes in BB rats. Diabetes 34, 197-199, 1985. 23. Scott, F. W.. Mongeau, R., Kardish, M., Hatina, G., Trick, K. D.. and Wojcinski, Z., Diet can prevent diabetes in the BB rat. Diabetes 34, 1059-1062, 1985. 24. Satoh, J., Shintani, S., Oya, K., Tanaka, S., Nobunaga. T.. Toyota, T., and Goto. Y.. Treatment with streptococcal preparation (OK-432) suppresses anti-islet autoimmunity and prevents diabetes in BB rats. Dinbetes 37, 188-194, 1988. 2.5. Oldstone, M. B., Prevention of type I diabetes in nonobese diabetic mice by virus infection. Scierwe
239, 500-502,
1988.
26. Dyrberg. T.. Schwimmbeck, P. L., and Oldstone, M. B., Inhibition of diabetes in BB rats by virus infection. J. Clin. Invest. 81, 928-931, 1988. 27. Koike, T., Itoh, Y., Ishii, T., Ito, I., Takabayashi, K.. Maruyama, N., Tomioka, H., and Yoshida, S.. Preventive effect of monoclonal anti-L3T4 antibody on development of diabetes in NOD mice. Diabetes 36, 539-541, 1987. 28. Like. A. A., Biron, C. A., Weringer, E. J., Byman, K., Sroczynski, E.. and Guberski, D. L.. Prevention of diabetes in BioBreeding/Worcester rats with monoclonal antibodies that recognize T lymphocytes or natural killer cells. .I. Exp. Med. 164, 1145-1159. 1986. 29. Nishimoto, K., Kikutani, H., Kanamura, K.. and Kishimoto. T., Prevention of autoimmune insulitis expression of I-E molecules in NOD mice. Nature (London) 328, 432-434, 1987. 30. Like, A. A., Butler, L., Williams. R. M., Appel, M. C.. Weringer, E. J.. and Rossini, A. A., Spontaneous autoimmune diabetes mellitus in the BB rat. Diabetes 31, 7-13, 1982. 31. Rossini, A. A., Slavin, S., Woda, B. A., Geisberg. M., Like, A. A., and Mordes, J. P., Total lymphoid irradiation prevents diabetes mellitus in the Bio-Breeding/Worcester (BB/W) rat. Diabetes 33, 543-547,
1984.
32. Like, A. A., Dirodi, V., Thomas, S.. Guberski, D. L., and Rossini, A. A., Prevention of diabetes mellitus in the BB/W rat with cyclosporin A. Amer. J. Patho/. 117, 92-97, 1984. 33. Nerup, J.. Bendtzen, K., and Mandrup Poulsen, T., A role for cyclosporin A in the treatment of insulin-dependent diabetes mellitus? Diabetic Med. 2, 441-446, 1985. 34. Rossini. A. A., Mordes, J. P., Pelletier. A. M., and Like, A. A., Transfusions of whole blood prevent spontaneous diabetes mellitus in the BB/W rat. Science 219, 975-977, 1983. 35. Mordes, J. P., Gallina, D. L., Handler, E. S., Greiner, D. L., Nakamura, N., Pelletier, A., and Rossini, A. A., Transfusions enriched for W3/25 + helper/induced T lymphocytes prevent spontaneous diabetes in the BBW rat. Diabefologia 30, 22-26, 1987. 36. Rossini, A. A., Mordes, J. P., Greiner, D. L., Nakano. K., Appel, M. C., and Handler, E. S., Spleen cell transfusion in the Bio-Breeding/Worcester rat: Prevention of diabetes. major histo-
S98
37. 38.
39. 40. 41. 42.
WILLIAM
J.
RII.Fl
compatibility complex restriction, and long-term persistence of transfused cells. J. C‘lin. Ingest. 77, 1399-1401. 1986. Rossini, A. A.. Faustman, D.. Woda. B. A.. Like, A. A., Szymanski, I., and Mordes. J. I’., Lymphocyte transfusions prevent diabetes in the Bio-Breedingiworcester rat. .I. Clirr. /nre.cf. 74, 3946, 1984. Yasumizu. R., Sugiura, K., Iwai, H.. Inaba, M., Makino, S., Ida, T., Imura, H.. Hamashima, Y _. Good, R. A., and Ikehara. S.. Treatment of type 1 diabetes mellitus in non-obese diabetic mice by transplantation of allogeneic bone marrow and pancreatic tissue. Proc. Nat/. Acad. Sci. USA 84, 65556557. 1987. Naji, A.. Silvers. W. K.. Kimura. H., Anderson, A. 0.. and Barker, C. F.. Influence of islet and bone marrow transplantation on the diabetes and immunodeficiency of BB rats. Metabolism 32. 62-68, 1983. Yale, J. F.. Grose, M., Seemayer. T. A., and Marliss, E. B., Diabetes prevention in BB rats by frequent blood withdrawal started at a young age. Diabetes 37, 327-333, 1988. Yamada, K.. Nonaka. K.. Hanafusa, T., Miyazaki, A., Toyoshima, H., and Tarui, S., Preventive and therapeutic effects of large-dose nicotinamide injections on diabetes associated with insulitis. Diubetes 31, 749753, 1982. Cavanaugh, J., Chopek. M., Binimelis, J., Seiva, A., and Barbosa, J., Buffy coat transfusions in early type I diabetes. Diabetes 36, 1089-93. 1987.
Received July 7, 1989: accepted July 21. 1989
IMMUNOLOGY
AND
Insulin
IMMlINOPATHOLOGY
53. sY?-s% (1989)
Dependent Diabetes Mellitus, Autoimmune Disorder?’
an
WILLIAM J. RILEY Department
of Pathology,
University
qf Florida,
Gainesville,
Florida
32610
During the last 25 years the concept of a chronic autoimmune process leading to the development of insulin dependent diabetes (IDD) has emerged. The presence of two animal models for IDD, the BB rat and the NOD mouse, has improved our ability to understand the process leading to p cell destruction. The hallmark of an autoimmune disease is the characteristic pathologic lesion of mononuclear infiltration of the pancreatic islets. Further histologic studies of the diabetic pancreas have identified the type of cells infiltrating the islets and led to the concept of pancreatic p cells capable of presenting antigen. The initial description of linkage disequilibrium of HLA DR3 and DR4 alleles with IDD has now progressed to the molecular level with the identification of residue 57 of the HLA DQ p chain as crucial to the genetic predisposition to IDD. Autoantibodies to cytoplasmic antigens (ICA), surface antigens, or a membrane protein of 64 kDa identified by immunoprecipitation, autoantibodies to secreted products such as insulin and proinsulin, and autoantibodies that are cytotoxic to cultured p cells are islet specific autoantibodies that have been described. Some are probably only markers of immunologic activity; others might participate in the destruction itself. The use of ICA as a screening tool has been successful in identifying individuals prior to the onset of IDD. Widespread cellular immunological defects have been identified both in animal models and in man. In the BB rat, a seeming paradox of severe immunodeficiency occurs in an animal with autoaggressive destruction of p cells. More subtle defects in immunoregulation have been described in the NOD mouse and in human IDD. The response of IDD in both animal models and in man to immunomodulation and to immunosuppression offers further evidence of an immunologically mediated disease. However, some therapies in the animal models, not typically considered immunologic, such as protein restriction and insulin therapy, have prevented IDD. The possibility of intervening prior to the onset of clinical disease at the level either of the initial process of recognition of the pancreatic p cell as a target organ or of the effector mechanism is approaching a reality in human IDD. “i 1989 Academic PXS, IIIC.
Insulin dependent diabetes mellitus (IDD) is one of the most common chronic illnesses in childhood. Effective therapy of IDD demands a lifelong commitment to daily multiple insulin injections and blood glucose determinations, as well as dietary and exercise constraints. Such therapy is not curative but is aimed at maintaining normoglycemia. Nevertheless, the morbidity and mortality remain high and life expectancy is shortened. Any approach to a cure or prevention of IDD will need to be directed against the underlying pathologic process (1). The onset of clinical disease represents the end stage or result of a chronic ’ Supported by a grant from the National Institutes of Health (AM36151) and a Clinical Research Center grant (RR 0082). Dr. Riley is the recipient of an NIH Research Career Development Award (AM01421). Presented as part of a symposium entitled “Autoimmunity and Immunointervention,” March 5-8, 1989, Scottsdale, AZ. S92 0090-1229/89 $1.50 Copyright 0 1989 by Academic Press, Inc. All rights of reproduction in any form reserved
IDD: AUTOIMMUNE
s93
DISORDER?
autoimmune destruction of the insulin-producing pancreatic l3 cells. Several features characterize IDD as an autoimmune disease: mononuclear infiltration of the pancreatic islets (insulitis) (2-5), association with the immune response genes of the major histocompatibility complex on chromosome 6, presence of a number of islet specific autoantibodies (1,6), defects in cell-mediated immunity (7), response to immunotherapy (8), and the frequent occurrence of other autoimmune diseases in affected individuals or in their family members (9). The natural history of the latent or presymptomatic phase of IDD (1) can be summarized briefly. In a genetically predisposed individual, an immunologically mediated destruction of the p cells gradually results in l3 cell elimination, loss of insulin secretion, and the onset of clinical disease. The ongoing immunologic process that is characteristic for the “prediabetic” phase can be identified by the presence of autoantibodies to a cytoplasmic antigen (ICA), to an immunoprecipitable protein of approximately 64 kDa (64KA), and to native insulin (IAA) (1, 6, 10). l3 cell function can be evaluated by determining the insulin response to glucose in an intravenous glucose tolerance test and oral glucose test (Table 1). There are still major gaps in our understanding of this autoimmune process. Initially, IDD was found to be associated with HLA B8 and B15. However, the linkage was later shown to be with HLA DR3 and DR4. Nearly 95% of IDD patients have a DR3 and/or DR4 allele, with 40% being DR3/4 heterozygotes. The DR4 association could be further subdivided by RFLP of genes of the DQP chain (DQw3) into a protective form, DQw3.1, and a susceptible form, DQw3.2 (3-5). Most recently the presence of a noncharged amino acid at position 57 of the DQp chain has been shown to be associated with IDD (4), while aspartic acid at that position was neutral or negatively associated with IDD. More than 90% of Caucasian patients with IDD possessed no alleles with a DQl3 aspartic acid at position 57 (4). Thus, the antigen binding affinity might possibly be influenced by the charge of the amino acid at this critical position. In conflict with this hypothesis is the observation that alleles from Chinese IDD patients were not associated with nonaspartic acid at DQP position 57. Alternatively. these particular HLA associations may be important in the regulation of the immune system. We recently described the increased relative antigen density of DR on the surface of T lymphocytes in patients who were HLA DR3/DR4 heterozygotes (7). The ability to identify future IDD patients months to years before onset of the disease by the detection of islet cell autoantibodies has documented the chronicity of the latent phase of this disease (1). Autoantibodies to cytoplasmic antigens of TABLE POSSIBLE
EXPLANATIONS
FOR
1 HLA ASSOCIATION
IN
IDD
1. Linked marker to the “diabetes gene” 2. Structural variation in HLA molecules a. Immune response Differential antigen peptide binding Differential expression of specific T cells, “hole” in T cell repertoire b. Molecular mimicry 3. Regulatory variation in expression of HLA molecules
s94
WILI.IAM
.J. RI1.F.k
all cells in the islet (ICA) and to insulin have been most widely used to detect prediabetes ( 1). In our studies, the presence of ICA detected before the age of 10 years in relatives of IDD patients was found to have an actuarial estimate of probability of developing IDD close to 100% after 5 years. Another significant factor in the prediction of IDD was the titer of ICA. The higher the titer, the higher the risk for developing IDD. However, ICA are reactive to an antigen(s) common to all islet cells, not only to the fi cells. Thus, neither ICA nor IAA are likely candidates for a role in the destruction of the p cells or for being the primary antigen. In our experience, IAA appear to reflect more active disease (6). The presence of ICA and IAA was associated more frequently with impaired insulin responses to an intravenous glucose infusion than the presence of ICA alone (6). The insulin responses to iv glucose and the concentration of IAA have been combined in a linear model to predict the time to onset of IDD ( 1I). In the rat, autoantibodies to a surface antigen(s) have been shown to have p cell specificity and thus might participate in the disease process (12). Recently, 64KA have been documented in the prediabetic phase of man and in both animal models of IDD, the NOD mouse and the BB rat (10, 13, 14). In a comparison of the three autoantibodies, ICA, 64KA, and IAA, 64KA were present in 20 of 23 sera from individuals who subsequently developed IDD, whereas ICA were found in 17 of 23 and IAA in I 1 of 23 (15). The ubiquitous and conserved nature of this antigen across species, the membrane and possibly surface nature of this protein, and the detection of 64KA before other islet specific autoantibodies offer plausible arguments for a primary antigen. Not only has the antigen (5) been elusive, but the mechanisms by which the pancreatic p cells are specifically recognized by the immune system and subsequently destroyed are also unknown. In an interesting study using transgenic expression of the SV40 gene in the pancreas of mice, the delayed expression of the SV40 antigen resulted in the lack of tolerance to this antigen (16). This delayed expression of an antigen might contribute to the pathogenesis. Immunohistochemical staining of human pancreases from newly diagnosed IDD patients has demonstrated aberrant expression of class I and class II antigens on p cells. Thus one could hypothesize that after an environmental trigger such as a viral infection and consequent induction of class II antigens, the /3 cells will be capable of presenting their own antigens in an immune response (17). In addition, we have confirmed the study of Gotfredsen et al. (18) in the BB rat and successfully used insulin therapy prior to the onset of IDD in the NOD mouse to prevent IDD, presumably by decreasing /3 cell activity and down-regulating the p cell antigen or by a direct effect of insulin on the immune system. One of the seeming paradoxes of autoimmune diseases is the development of an “anti-self’ process in individuals with primary immune deficiency disorders. Nowhere is this so apparent as in the BB rat. These animals have severely deficient numbers and function of T cells. They are unable to reject skin grafts and respond poorly in an allogeneic MLR or to mitogens (19). Also, they display marked lymphopenia with an inverted CD4 to CD8 ratio and lack the subset of cells defined as RT6 (19). Yet the p cells are destroyed. In man and the NOD mouse, the defects appear to be more subtle in comparison. Suppressor cell function is
IDD: AUTOIMMUNE
s95
DISORDER?
depressed and the T lymphocytes from NOD mice do not produce IL-1 to the same degree as other mice (20). We have recently found both a decreased number and function of the CD4 + CD45R - T cell population reflected by a defect in the ability of T cells to provide help in a pokeweed mitogen-driven T-B coculture assay in ICA+ prediabetic individuals. In addition, lymphocytes from these individuals produce less interferon-y than controls in response to mitogenic stimulation. How these defects relate to the final effector mechanism and how p cell destruction can be prevented remain to be determined. Table 2 summarizes many of
TABLE Agent or procedure (Ref. )
IDD model
2 Result
Silica (21, 22)
BB rats
Marked reduction of IDD
Insulin therapy (18)
BB rats NOD mice NOD mice BB rats NOD mice
Prevention of IDD
Protein-restricted diet (23) Streptococcal Prep. OK-432 (24) LCM virus (25, 26)
Mab to NK cells (28)
NOD mice BB rats BB rats
Reduces frequency of IDD Prevention of IDD and insulitis Complete prevention of IDD and insulitis Prevention of insulitis Prevention of IDD
I-E transgenic (29) Neonatal thymectomy (30)
NOD mice BB rats NOD mice
No insulitis Reduces frequency of IDD
Total lymphoid irradiation (3 I) Cyclosporins (32, 33)
BB rats NOD mice BB rats NOD mice
Lymphocyte transfusions (34-37) Allogeneic bone marrow transplantation (38, 39) Repeated phlebotomies (40)
BB rats
Reduces frequency of IDD Prevention and partial reversal of IDD Reduces frequency of IDD
Nicotinamide
Mab to CD4 (27, 28)
(40)
NOD mice BB rats
NOD mice BB rats
Prevention of IDD
BB rats
Prevention of IDD
NOD mice
Prevents IDD
Possible mechanism Macrophage inactivation or depletion Decreased p cell antigen expression 9 Increased CD8 cells? Decreased CD4 cells Elimination
of CD4
Elimination cells
of NK
‘3 Prevents cell-mediated immunity Immunosuppression Immunosuppression Reconstitution with normal immune cells Reconstitution with normal immune cells Stimulation immune removal positive
of system; of CD4 cells ?
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WILLIAM
J. RIl.F.1’
the prevention studies carried out in animal models. In man, no prevention trials have been done, although immunosuppression with steroids, azathioprine (Imuran, Burroughs-Wellcome Co.), cyclosporine (Sandimmune, Sandoz Pharmaceuticals Corp.), or immunotherapy using intravenous immunoglobulin or lymphocyte transfusions have been attempted in patients with newly diagnosed IDD (42). Immunosuppression has been shown to prolong the l3 cell function but complete remission has not been sustained for more than 3 years. In our studies using azathioprine and high dose steroid induction, we have demonstrated significant preservation of l3 cell function (8). A second remission was established with a second high dose methylprednisolone induction, albeit of limited duration, in one boy who remained in an insulin-free remission for 3 years. The major difficulty with treating patients at the onset of IDD is that this stage is the end point of the presymptomatic (latent) phase of the disease and very few l3 cells remain to be salvaged. Thus the approach to preventing the clinical expression of IDD needs to be done during the prolonged latent phase. As we understand the natural history and have improved our prognostic markers of the prediabetic state. prevention in man may now be possible. REFERENCES I. Riley, W. J., Winter, W. E., and Maclaren, N. K.. Identification of insulin-dependent diabetes mellitus before the onset of clinical symptoms. J Pediarr. 112, 314316, 1988. 2. Gepts, W., Islet morphology in type I diabetes. Behring Inst. Mitt. 123, 39-41, 1984. 3. Henson, V., Maclaren. N. K., Riley, W. J., and Wakeland, E. K., Polymorphisms of DQ beta genes in HLA-DR4 haplotypes from healthy and diabetic individuals. 1mmunogenetic.s 25, 152160. 1987. 4. Todd. J. A., Bell, J. I., and McDevitt, H. O., HLA-DQ beta gene contributes to susceptibility and resistance to insulin-dependent diabetes mellitus. Nature (London) 329, 599-604. 1987. 5. Nepom, B. S., Schwarz, D.. Palmer. J. P.. and Nepom, G. T.. HLA-DQ alpha- and beta-chains produce hybrid molecules in DR3/4 heterozygotes. Diubetes 36, 114-l 17, 1987. 6. Atkinson, M. A.. Maclaren, N. K., Riley, W. J., Winter, W. E.. Fisk, D. D., and Spillar, R. P., Are insulin autoantibodies markers for insulin-dependent diabetes mellitus‘! Diabetes 35,894-898, 1986. 7. Hitchcock, C. L.. Riley, W. J.. Alamo, A., Pyka, R.. and Maclaren. N. K.. Lymphocyte subsets and activation in prediabetes. Diabetes 35, 1416-1422, 1986. 8. Silverstein, J. H., Maclaren, N. K., Riley, W. J., Spillar, R., Radjenovic. D., and Johnson, S., Immunosuppression with azathioprine and prednisone in recent-onset insulin-dependent diabetes mellitus. N. Engl. J. Med. 319, 599-604, 1988. 9. Maclaren, N. K., and Riley, W. J., Thyroid gastric and adrenal autoimmunities associated with insulin dependent diabetes mellitus. Diabetes Cure 8, 34-38, 1985. 10. Baekkeskov, S., Landin. M., Kristensen. J. K., Srikanta, S., Bruining, G. J., Mandrup Pot&en, T., de Beaufort, C., Soeldner, J. S., Eisenbarth, G. S.. and Lindgren, F., Antibodies to a 64,000 Mr human islet cell antigen precede the clinical onset of insulin-dependent diabetes. J. C/in. Invest.
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Received July 7, 1989: accepted July 21. 1989