The thyroid "microsomal" antibody revisited. Its paradoxical binding in vivo to the apical surface of the follicular epithelium.

We have shown that thyroid monolayers derived from the glands of patients with autoimmune thyroid disease have immunoglobulin (Ig) bound to their surface. This appears to have been deposited in vivo rather than during preparation of the monolayers, a view supported by our finding of such deposits on the apical margin of follicular cells in sections cut from these glands and stained with conjugated anti-immunoglobulin. It is likely that these deposits represent specific binding of so-called "microsomal" autoantibodies to the surface of the thyroid cells in vivo since staining of partially disrupted follicles ("half-melons") with Hashimoto serum containing microsomal autoantibodies in the indirect immunofluorescence (IFL) test, localized the antigen on the apical surface of the cells lining the follicular cavity. Thus, paradoxically, although the antigen is relatively inaccessible, autoantibodies do reach and combine with the thyroid surface in vivo and may therefore play a role in pathogenesis.

The synaptic vesicle-associated protein amphiphysin is the 128-kD autoantigen of Stiff-Man syndrome with breast cancer.

Stiff-Man syndrome (SMS) is a rare disease of the central nervous system (CNS) characterized by progressive rigidity of the body musculature with superimposed painful spasms. An autoimmune origin of the disease has been proposed. In a caseload of more than 100 SMS patients, 60% were found positive for autoantibodies directed against the GABA-synthesizing enzyme glutamic acid decarboxylase (GAD). Few patients, all women affected by breast cancer, were negative for GAD autoantibodies but positive for autoantibodies directed against a 128-kD synaptic protein. We report here that this antigen is amphiphysin. GAD and amphiphysin are nonintrinsic membrane proteins that are concentrated in nerve terminals, where a pool of both proteins is associated with the cytoplasmic surface of synaptic vesicles. GAD and amphiphysin are the only two known targets of CNS autoimmunity with this distribution. This finding suggests a possible link between autoimmunity directed against cytoplasmic proteins associated with synaptic vesicles and SMS.

Serum transforming growth factor ß1 during diabetes development in non-obese diabetic mice and humans.

Recent data show that regulatory cells with transforming growth factor (TGF)-ß1-dependent activity are able to restore self-tolerance in overtly diabetic non-obese diabetic (NOD) mice. Thus, TGF-ß1 seems to have a relevant role in protection from autoimmune diabetes. Our aim was to investigate the possible significance of serum TGF-ß1 measurement in the natural history of diabetes in NOD mice, as well as in children positive for at least one islet-related antibody. Serum TGF-ß1 (both total and active) was measured by enzyme-linked immunosorbent assay at monthly intervals in 26 NOD mice during the spontaneous development of diabetes and, on a yearly basis, in nine siblings of patients with type 1 diabetes (T1D) with a follow-up of 4 years. Diabetes appeared between the 12th week of age and the end of the study period (36 weeks) in 17 mice. TGF-ß1 serum level variations occurred in the prediabetic period in both NOD mice and humans and diabetes diagnosis followed a continuing reduction of active TGF-ß1 (aTGF-ß1) serum levels. In mice, aTGF-ß1 serum levels measured at 4 weeks of age correlated positively with severity of insulitis, and negatively with percentage of insulin-positive cells. Our findings suggest that in NOD mice serum TGF-ß1 levels during the natural history of the diabetes reflect the course of islet inflammation. The measurement of aTGF-ß1 in islet-related antibody-positive subjects may provide insights into the natural history of prediabetic phase of T1D.

Human T-cell clones from autoimmune thyroid glands: specific recognition of autologous thyroid cells.

The thyroid glands of patients with autoimmune diseases such as Graves' disease and certain forms of goiter contain infiltrating activated T lymphocytes and, unlike cells of normal glands, the epithelial follicular cells strongly express histocompatibility antigens of the HLA-DR type. In a study of such autoimmune disorders, the infiltrating T cells from the thyroid glands of two patients with Graves' disease were cloned in mitogen-free interleukin-2 (T-cell growth factor). The clones were expanded and their specificity was tested. Three types of clones were found. One group, of T4 phenotype, specifically recognized autologous thyroid cells. Another, also of T4 phenotype, recognized autologous thyroid or blood cells and thus responded positively in the autologous mixed lymphocyte reaction. Other clones derived from cells that were activated in vivo were of no known specificity. These clones provide a model of a human autoimmune disease and their analysis should clarify mechanisms of pathogenesis and provide clues to abrogating these undesirable immune responses.

Progress toward standardization of cytoplasmic islet cell-antibody assay.

Cytoplasmic islet cell autoantibodies (ICAs) of 13 coded sera were determined by 26 laboratories. ICAs were determined by 24 laboratories according to a standard protocol based on the conventional indirect-immunofluorescence technique on cryostat sections of human pancreas. In addition, these 24 laboratories had performed any of 8 modifications of the assay. Test samples were titrated to end point, and the results obtained with the different methods were compared with those obtained by the standard protocol. The remaining 2 laboratories used either exclusively pancreatic sections of monkey instead of human as substrate (lab 23) or applied immunohistochemical staining (lab 22). By following the standard protocol, interlaboratory concordance was greater than 90% for the presence or absence of islet cell antibodies in 7 of the 13 samples circulated. However, a wide variability of titers was recorded, ranging from negative to 128. Of the modifications, prolonged incubation in the presence of aprotinin was performed by 10 laboratories and was found to improve the sensitivity in 57 of 70 (81%) determinations with samples that had been ICA positive by the standard protocol. Improved sensitivity was also noted by 2 laboratories with sections of monkey pancreas. Acetone-fixed sections, used by 6 laboratories, or a two-color immunofluorescence method, applied by 3 laboratories, did not change the titers in 27 of 35 (77%) and 14 of 25 (56%) determinations with samples that had been ICA positive by the standard protocol. In contrast, heat inactivation of the samples before testing, performed by 5 laboratories, resulted in a decrease in titers in 25 of 39 (64%) determinations.(ABSTRACT TRUNCATED AT 250 WORDS)

Islet cell antibodies identify latent type I diabetes in patients aged 35-75 years at diagnosis.

One hundred fifty-four selected patients with nonketotic diabetes diagnosed between the ages of 35 and 75 yr and treated with diet or oral hypoglycemic agents for at least 1 yr were investigated for parameters of glycemic control (weight loss, blood glucose, and glycosylated hemoglobin), islet cell function (fasting and glucagon-stimulated C-peptide responses), and immunologic markers of insulitis (total ICA and CF-ICA) or autoimmunity (thyroid and gastric antibodies). These parameters were all repeated in 9 of 22 ICA-positive patients after a 2-yr follow-up and correlated with secondary drug failure. The antibody tests were also done on 51 nondiabetic controls matched for age and body weight. The 22 (14%) diabetic subjects having positive islet cell antibodies (ICA) included more women than men with a shorter duration of symptoms, lower body weight, more associated thyroid autoimmunity, and a tendency to have more type I diabetes in their families, although glycemic control, age at onset, and family history of type II diabetes were the same as in the 132 ICA-negative cases. Patients with ICA had lower initial C-peptide levels and showed little rise after glucagon stimulation. Beta cell function deteriorated significantly during the 2-yr follow-up in 9 of 22 positive patients and more ICA-positive patients required insulin. It is suggested that these latent type I diabetic patients are characterized by persistent ICA, progressive loss of beta cells, and a high frequency of thyrogastric autoimmunity. The determination of ICA may be of clinical value in the diagnosis and treatment of nonketotic diabetes with onset in later life.

Progression to type I diabetes in autoimmune endocrine patients with islet cell antibodies.

In an 11-yr screening program carried out on serum samples sent to an autoimmune serology laboratory, 158 patients with clinical or subclinical autoimmune endocrine manifestations and islet cell antibodies (ICAs) in the absence of overt diabetes were identified and followed for the development of insulin-dependent (type I) diabetes. Twenty-two (13.9%) developed type I diabetes in a follow-up of up to 12 yr (mean +/- SE 4.8 +/- 3.2 yr). The probability of being free of type I diabetes was 69.8% at 10 yr after the first detection of ICAs. Progression to disease was influenced by 1) the amount of ICAs represented by high titers (63% of those with ICAs greater than or equal to 20 Juvenile Diabetes Foundation units being free of type I diabetes at 10 yr), ICA persistency (59% being free of type I diabetes; P less than 0.02 vs. nonpersistent ICA), and complement-fixing (CF)-ICAs (63% being free of type I diabetes; P less than 0.05 vs. non-CF-ICA); 2) the coexistence of insulin autoantibodies (IAAs) (25% being free of type I diabetes; P less than 0.005 vs. IAA-); and 3) a positive family history (1st-degree relative) for type I diabetes (32% being free of type I diabetes; P less than 0.005 vs. no family history). There was a trend for diabetes to develop earlier in males of a younger age. No relationships were found with the number, type, or clinical expression of the associated autoimmunities or with a family history of such disorders.(ABSTRACT TRUNCATED AT 250 WORDS)

High level of concordance between assays for glutamic acid decarboxylase antibodies. The First International Glutamic Acid Decarboxylase Antibody Workshop.

Glutamic acid decarboxylase antibodies (GADAbs) are being increasingly used in clinical and research programs for the prediction and classification of insulin-dependent diabetes mellitus (IDDM). A number of different assay formats for the measurement of GADAbs have been reported, but the degree of concordance between assays is unknown. In this study, GADAbs were measured on 16 coded sera in 34 assays to examine concordance between GADAb assays and establish the feasibility of an international GADAb standard of measurement unit. The 16 lyophilized coded samples consisted of sera from healthy control subjects (n = 2), IDDM patients (n = 3), a patient with polyendocrine autoimmunity (n = 1), and duplicate dilutions of plasmapheresis serum from a patient with stiff-man syndrome (SMS). A high level of concordance was found in the ranking of GADAb levels (P = 0.99, Friedman's test) in the samples. Thirteen (38%) assays could reproducibly distinguish dilutions of SMS serum and detect GADAbs in all IDDM and polyendocrine autoimmunity sera tested. Although assessed on only four samples, disease specificity was 100% in 29 assays. The majority of assays that immunoprecipitated radiolabeled GAD gave high results for sensitivity and specificity. Enzyme-linked immunosorbent assays and assays using immunofluorescence were generally less sensitive. Several assays, in particular those measuring GAD enzymatic activity immunoprecipitated in fluid phase from rat brain homogenate, showed a prozone-like phenomenon in the SMS dilution curve. Interpolation of results from a standard curve into workshop units resulted in relatively low scatter in samples with lower levels of GADAbs. Hence, the use of an international reference serum to enable comparison of results between laboratories appears feasible.(ABSTRACT TRUNCATED AT 250 WORDS)

Prediction of IDDM in the general population: strategies based on combinations of autoantibody markers.

Strategies for assessing risk of progression to IDDM, based on single and combined autoantibody measurement, were evaluated in 2,855 schoolchildren (median age 11.4 years) and 256 children with newly diagnosed IDDM (median age 10.2 years), recruited to a population-based study in the Oxford region. In 256 children with IDDM, levels of antibodies > or =97.5th centile of the schoolchild population were found in 225 (88%) for islet cell antibodies (ICAs), in 190 (74%) for antibodies to GAD, in 193 (75%) for antibodies to protein tyrosine phosphatase IA-2 (IA-2), and in 177 (69%) for autoantibodies to insulin (IAAs). Estimates of risk of progression to IDDM within 10 years, derived by comparing the distribution of antibody markers in the two populations (schoolchildren and children with IDDM), were 6.7% (ICAs), 6.6% (GAD antibodies), 5.6% (IA-2 antibodies), and 4.8% (IAAs) for schoolchildren with levels above the 97.5th centile, increasing to 20, 23, 24, and 11%, respectively, for antibody levels >99.5th centile. Most children with IDDM had multiple antibody markers, and 89% of those diagnosed over age 10 years had > or =2 antibodies above the 97.5th centile, as compared against 0.7% of schoolchildren, in whom this combination gave a 27% 10-year estimated risk of IDDM. Risk increased but sensitivity fell as combined antibody thresholds were raised, or the number of antibodies above the threshold was increased. Strategies based on detection of > or =2 antibodies with primary testing for GAD and IA-2 antibodies and second line testing for ICAs and/or IAAs were evaluated. Detection of at least two markers selected from GAD antibodies > or =97.5th centile and/or IA-2 antibodies > or =99.5th centile and/or ICAs > or =97.5th centile identified 0.25% of schoolchildren and 83% of children with newly diagnosed IDDM, with an estimated risk of 71% (95% CI 57-91). Although confirmation from prospective studies is still needed, this analysis suggests that antibody combinations can predict diabetes in the general population.

Correlation between residual beta-cell function and islet cell antibodies in newly diagnosed type I diabetes. Follow-up study.

To establish whether there is a correlation between the autoimmune response to the islets and beta-cell function during the initial stages of type I (insulin-dependent) diabetes, and islet cell antibody (ICA) titer and C-peptide levels (fasting and glucagon stimulated) were determined in 39 newly diagnosed patients at onset of diabetes and every 3-6 mo for 2 yr. ICAs were detected in 74% of the patients, and beta-cell function was detected in 84% of the patients at onset. The ICA+ and ICA- groups had similar C-peptide values at diagnosis and at 3 mo, but from 6 mo on, the ICA+ group consistently showed a tendency to lose C-peptide secretory capacity more quickly when assessed by fasting and glucagon-stimulated C-peptide levels (ICA+ vs. ICA- fasting C-peptide levels at 18 and 24 mo, P = .013 and .017, respectively; ICA+ vs. ICA- glucagon-stimulated C-peptide levels at 6, 18, and 24 mo, P = .023, .007, and .028, respectively). The initial ICA titer had the highest predictive value on the outcome of beta-cell function (P = .04), and patients with complement-fixing ICAs did not behave differently from the general ICA+ group. This correlation between beta-cell function and ICA titer supports the role of autoimmunity in the pathogenesis of type I diabetes and has important implications for the design of immunotherapy trials.

Organ-specific autoimmunity and HLA-DR antigens as markers for beta-cell destruction in patients with type II diabetes.

Islet cell antibodies (ICAs), thyrogastric antibodies, and HLA-DR antigens were determined in 204 patients with type II (non-insulin-dependent) diabetes controlled with diet and/or oral hypoglycemic agents (NIR) and in 108 age-matched patients who required insulin to control their hyperglycemia (IR). beta-Cell function measured as C-peptide response to glucagon was evaluated in relation to the presence of ICAs and HLA-DR antigens. The IR patients differed from the NIR patients with respect to higher frequency of ICAs (P less than .001), thyroid antibodies (P less than .02), and the HLA antigen DR4 (P less than .02). The highest frequency of ICAs and thyroid antibodies was observed in female insulin-treated subjects (51.2 and 46.4%). Patients who were heterozygous for HLA-DR3/DR4 showed significantly higher frequency of ICAs (P less than .01) and complement-fixing ICAs (P less than .001) than patients without the heterozygous form DR3/DR4. Neither the presence of ICA alone nor DR3/DR4 alone was associated with a significant impairment of beta-cell function. However, when both ICA and DR3/DR4 were present in a diabetic individual, beta-cell function was markedly impaired (P less than .001), suggesting that both genetic and autoimmune factors are necessary to facilitate the process leading to beta-cell destruction of the patients. Our findings suggest that type II diabetes is a heterogeneous disorder including at least two major subgroups, which can be further characterized by HLA-DR antigens and organ-specific antibodies.

Can future type I diabetes be predicted? A study in families of affected children.

This article examines the risk of type I (insulin-dependent) diabetes in siblings of affected children, in relation to HLA genotypes. The 288 available siblings of 160 diabetic probands were grouped according to the number of HLA haplotypes in common with their probands. HLA-identical siblings (both haplotypes in common) have an approximately 100 times greater risk of developing the disease than that in the general population, and this risk is significantly higher than that in haplo-identical siblings (one haplotype in common) P = 0.008). Thus, in Northern European populations, some 30% of HLA-identical siblings are expected to be diabetic by the age of 30 yr. The risk in nonidentical siblings (neither haplotype in common) is not significantly increased. These findings carry implications for genetic counseling and research.

Antibodies to islet 37k antigen, but not to glutamate decarboxylase, discriminate rapid progression to IDDM in endocrine autoimmunity.

Apart from islet cell antibodies (ICAs), antibodies to glutamate decarboxylase (GAD), insulin autoantibodies (IAAs), and a novel islet antigen (37k antigen) are potential markers for insulin-dependent diabetes mellitus (IDDM). GAD is also an antigen in stiff-man syndrome (SMS), and both SMS and IDDM are associated with ICAs and autoimmunity to other endocrine organs. We investigated possible links between antibody responses to islet antigens with autoimmunity to other endocrine organs and determined which specific antibodies can identify individuals who progress to IDDM. Antibodies to GAD were detected in > or = 90% of both diabetic and nondiabetic patients with ICAs and other endocrine autoimmunity, in 59% of ICA-positive IDDM patients without endocrine autoimmunity, in all patients with SMS, but in only 1-3% of healthy (nondiabetic) and autoimmune disease control subjects. GAD antibody levels were increased in ICA-positive IDDM patients with polyendocrine autoimmunity compared with those without. In contrast, antibodies to 37k antigen were only detected in patients who developed acute-onset IDDM. IAAs were also associated with IDDM. Thus, certain factors enhance antibody responses to GAD in polyendocrine autoimmunity, but this does not necessarily lead to development of IDDM or SMS. Antibodies to 37k antigen are strongly associated with acute-onset IDDM and are useful serological markers for disease.

Combined analysis of autoantibodies improves prediction of IDDM in islet cell antibody-positive relatives.

Prediction of insulin-dependent diabetes mellitus (IDDM) is still largely based on islet cell antibodies (ICAs), but it may be improved by combined analysis with other humoral markers. We examined autoantibodies to insulin (IAAs), glutamic acid decarboxylase (GAD), and M(r) 37,000 and M(r) 40,000 fragments of islet antigens (37 and 40 kDa) together with ICA subtypes in 101 family members with ICAs > or = 10 Juvenile Diabetes Foundation units (JDF U) followed for up to 14 years, of whom 18 have developed IDDM. Life-table analysis showed a 43% risk of IDDM within 10 years for those with ICAs > or = 10 JDF U, rising to 53% for those with ICAs > or = 20 JDF U. The risk for ICAs > or = 10 JDF U was 62% in the family members in the youngest age quartile (< 13.2 years) and fell with increasing age to 4% in those > 40.7 years of age (P = 0.03). ICAs > or = 10 JDF U combined with IAAs gave a risk of 84% (P = 0.03 compared with IAA-), and ICAs > or = 10 JDF U combined with GAD antibodies gave a risk of 61% (P = 0.018). The risk for ICAs > or = 10 JDF U with antibodies to 37-kDa antigen was 76% (P < 0.0001). Risk increased with the number of autoantibodies, from 8% for ICAs alone to 88% with > or = 3 autoantibodies (14 cases detected) (P < 0.0001). The increased risk associated with multiple antibodies was observed independent of age.(ABSTRACT TRUNCATED AT 250 WORDS)

Lack of immunohistological changes in the islets of nondiabetic, autoimmune, polyendocrine patients with beta-selective GAD-specific islet cell antibodies.

We examined the pancreases from three nondiabetic, autoimmune, polyendocrine patients with islet cell antibodies (ICAs) and glutamic acid decarboxylase (GAD) antibodies who died without developing insulin-dependent diabetes mellitus (IDDM). All three patients had the beta-selective GAD-specific ICA subtype and antibodies to the GAD-derived 50 kD tryptic fragment. None had whole islet ICA or antibodies to the non-GAD-derived 37k islet antigen, which appear to be more closely associated with IDDM than antibodies to GAD. The three patients also were negative for insulin autoantibodies. Islets within pancreas from patients 1 and 2 appeared well preserved as assessed by hematoxylin and eosin staining. In these two patients, insulin content, as assessed by indirect immunofluorescence on cryostat sections, was normal. Patient 3 had a prolonged postmortem time, and the islet insulin content was reduced slightly. In all three pancreases, no evidence was found of increased human leukocyte antigen class I or de novo class II molecule expression on islet cells, and islet infiltration by T- or B-cells or macrophages was not detected. Islet capillary endothelial cells did not show signs of hypertrophy. No immunoglobulin or complement deposition within or around islets was found. These data indicate that humoral GAD autoimmunity does not necessarily associate with visible beta-cell damage.

Comparison of insulin autoantibodies in diabetes-related and healthy populations by precise displacement ELISA.

The second international workshop on insulin autoantibodies (IAAs) demonstrated improved concordance among laboratories with both radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA) when measurements were based on signals displaceable by preincubation with excess insulin. This feature has been incorporated into our original ELISA for IAAs, and the assay was used to compare IAAs in diabetes-related and healthy populations. The serum from a healthy islet cell antibody (ICA)+ and IAA+ subject was used to construct standard curves with and without preincubation with 1 U/ml human insulin. Reporting results in arbitrary displacement (delta +/- IAA) units derived from the standard curve improved precision and increased the specificity of the assay. Frequency analysis of the results from 200 control adults did not show a normal distribution, and cumulative frequency analysis demonstrated two populations: 10 of 200 (5%) control adults, 8 of 241 (3.3%) healthy schoolchildren, and 18 of 229 (7.9%) non-insulin-dependent diabetes mellitus (NIDDM) patients had IAAs greater than 12 delta +/- IAA units. On the same basis, we tested samples from 89 individuals in the prospective Bart's Windsor Family Study for insulin-dependent diabetes mellitus (IDDM), 31 of whom had ICAs greater than 5 Juvenile Diabetes Foundation (JDF) units. Of those with ICAs greater than 5 JDF units, 12 developed IDDM and 1 developed NIDDM in 10 yr of study. IAAs greater than 12 delta +/- IAA units were found in 6 of 12 (50%) who became diabetic and in 4 of 18 (22%) who remain healthy.(ABSTRACT TRUNCATED AT 250 WORDS)

Islet cell autoimmunity in type I diabetic patients after HLA-mismatched pancreas transplantation.

The aim of this study was to investigate a possible reenhancement of islet cell autoimmunity in type I (insulin-dependent) diabetic patients who received HLA-mismatched pancreas transplants from cadaveric donors and who underwent generalized immunosuppression. Circulating islet cell antibodies (ICA) and complement-fixing ICAs (CF-ICAs) have been tested at 1, 2, 3, 6, and 12 mo and at least once a year posttransplantation in 23 recipients of 25 transplants (22 simultaneous with kidney, 2 retransplants, 1 isolated; 23 segmental neoprene injected, 2 whole with enteric drainage). Patients were aged 35.3 +/- 1.9 yr with a duration of diabetes of 20.6 +/- 1.1 yr. Immunosuppression consisted of double or triple association of azathioprine, cyclosporin, and prednisone with or without temporary antilymphocyte globulins. The number of HLA-A and HLA-B compatibilities was none in 8 patients, one in 12 patients, two in 4 patients, and three in 1 patient. The mean follow-up was 4.0 +/- 0.4 yr/patient (range 0.4-7.2). ICAs were positive pretransplantation in 2 of 25 patients and reappeared 1-42 mo posttransplantation in another 7. In 6 patients, CF-ICAs were also positive. In 7 of 9 ICA+ patients the pancreas transplant failed; in 1 patient this occurred 4 mo before ICA reappearance, and in 6 patients it occurred 2-35 mo after the first detection of ICAs. Pancreas-transplant failure was significantly associated with the positivity for ICAs (P less than .05) and particularly for CF-ICAs (P less than .005). ICA positivity was transitory in 4 patients (2-27 mo) and persistent in the remaining 5 (up to 61 mo).(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies to GAD and tryptic fragments of islet 64K antigen as distinct markers for development of IDDM. Studies with identical twins.

Insulin-dependent diabetes mellitus (IDDM) is associated with antibodies to a 64,000-M(r) islet cell protein, at least part of which is identified as glutamic acid decarboxylase (GAD). These antibodies are detected as two distinct antibody specificities to 50,000-M(r) and 37,000/40,000-M(r) tryptic fragments of the autoantigen (50K and 37K antibodies, respectively). We determined the frequencies of antibodies to intact GAD, tryptic fragments of islet 64,000-M(r) antigen, islet cell antibodies (ICAs), and insulin autoantibodies (IAAs) in sera from 58 nondiabetic identical twins of patients with IDDM, of whom 12 subsequently developed diabetes. ICA, antibodies to intact GAD, and those to tryptic fragments were detected at similar frequencies in prediabetic twins (67-75%), but only 25% had IAA. Of 46 twins who remain nondiabetic, GAD antibodies, 50K antibodies, and ICA were detected in 6 (13%), 7 (15%), and 5 (11%), respectively, whereas only 1 (2%) possessed 37K antibodies and 2 (4%) had IAA. Eight of 9 twins with 37K antibodies and all 6 twins with ICA greater than 20 Juvenile Diabetes Foundation U have developed diabetes. Antibodies to GAD are sensitive markers for diabetes development but may also be present in genetically susceptible individuals who are unlikely to develop disease. Antibodies to 37,000/40,000-M(r) fragments of the 64,000-M(r) antigen or high-titer ICA were the best markers for diabetes development in these twins.

Genetic and immunologic factors in microvascular disease in type I insulin-dependent diabetes.

A detailed study of 133 subjects with insulin-dependent (type I) diabetes with severe microvascular disease has failed to substantiate the hypothesis that HLA factors influence the predisposition to this type of complication. A significant association between proliferative retinopathy and raised levels of circulating immune complexes was found. The distribution of insulin-binding levels in serum was similar to that in patients without complications. There was no correlation between insulin binding and the presence of immune complexes and no evidence was found that these complexes contained anti-insulin, anti-nuclear, or organ-specific antibodies. The distribution of insulin-binding levels in these subjects with diabetes of long duration was similar to that observed in 270 subjects with juvenile-onset short-duration type I diabetes. When the data were combined, significant associations between HLA-B8 and low/absent insulin binding levels were observed. HLA-BW62 was not associated with either high or low insulin-binding capacity. It is concluded that HLA genetic factors, insulin-binding capacity, and autoimmunity are unrelated to the pathogenesis of microvascular disease. Raised levels of circulating immune complexes may well be secondary to widespread tissue damage in diabetes of long duration.

Monoclonal antibodies defined abnormalities of T-lymphocytes in type I (insulin-dependent) diabetes.

Peripheral T-lymphocytes subsets have been investigated in 36 patients with type I (insulin-dependent) diabetes of varying duration, 18 patients with type II (non-insulin-dependent) diabetes, and in 23 healthy subjects, using six different monoclonal antibodies. At the time of diagnosis of type I diabetes, there was evidence of an increase in cytotoxic T-lymphocytes, a decrease in suppressor T-lymphocytes, but a normal proportion of helper/inducer T-lymphocytes. In six of seven newly diagnosed cases studied, there was evidence of an increased number of activated T cells. An increase in activated T-cells was also found in 5 of 10 genetically susceptible islet cell antibody positive unaffected siblings in type I diabetic probands. In type I diabetes of long standing, the total T-cell population was decreased, largely due to a marked decrease in helper/inducer T-lymphocytes. Type II diabetic patients showed no abnormalities in T-lymphocyte subsets, making it unlikely that hyperglycemia was responsible for the changes observed. These results suggest that an imbalance of T-lymphocyte regulation is an important feature of type I diabetes and lend support for an immunologic role in its early pathogenesis.