Islet autoantibody markers in IDDM: risk assessment strategies yielding high sensitivity

Identification of islet autoantigens offers the possibility that antibody tests other than islet cell antibodies may be used for assessing risk of insulin-dependent diabetes mellitus (IDDM). The aim of this study was to determine the combination of islet autoantibody markers that could identify most future cases of IDDM. Islet cell antibodies, antibodies to glutamic acid decarboxylase (GAD)65, 37,000/40,000 M(r) islet tryptic fragments, carboxypeptidase-H, and islet cell autoantigen (ICA)69 were measured in sera from 100 newly-diagnosed IDDM patients, 27 individuals prior to onset of IDDM, and 83 control subjects. Islet cell antibodies were detected in 88% of IDDM patients and 81% with pre-IDDM, GAD65 antibodies in 70% of IDDM patients and 89% with pre-IDDM, and antibodies to 37,000/40,000 M(r) islet tryptic fragments in 54% of IDDM patients and in 48% with pre-IDDM. The latter were found only in conjunction with islet cell antibodies and were more frequent in young onset cases. All 20 IDDM patients and the 3 pre-IDDM subjects who had islet cell antibodies without GAD65 antibodies had antibodies to 37,000/40,000 M(r) islet tryptic fragments, and all but one had disease onset before age 15 years. No sera strongly immunoprecipitated in vitro translated ICA69 or carboxypeptidase-H; 4% of patients had anti-ICA69 and 11% anti-carboxypeptidase-H levels above those of the control subjects. The findings suggest that none of the single antibody specificities are as sensitive as islet cell antibodies, but that a combination of GAD65 antibodies and antibodies to 37,000/40,000 M(r) islet tryptic fragments has the potential to identify more than 90% of future cases of IDDM.(ABSTRACT TRUNCATED AT 250 WORDS)

Disease sensitivity and specificity of 52 assays for glutamic acid decarboxylase antibodies. The Second International GADAB Workshop

There is increasing interest in the use of glutamic acid decarboxylase antibodies (GADAbs) for identification of subjects at increased risk of developing insulin-dependent diabetes mellitus (IDDM). However, considerable variation exists between laboratories in the reported frequency of GADAb in various clinical situations, and disease sensitivity and specificity have not yet been compared between assays. An international workshop was held in which 101 coded freeze-dried sera, including 39 from subjects with newly diagnosed IDDM, 32 from healthy control subjects, 4 from nondiabetic subjects with Graves' disease, and 4 from islet cell antibody-positive subjects, were analyzed in 52 assays (radiobinding assay [RBA], 26; enzyme-linked immunosorbent assay [ELISA], 19; and enzymatic immunoprecipitation assay [EIP], 7). The mean sensitivity for RBAs (76.2%) was higher than for ELISAs (36.5%) and EIPs (49.9%) (P < 0.01). The mean specificity was similar for each assay format (RBA, 89.4%; ELISA. 89.4%; and EIP, 92.3%). The lower sensitivities of the ELISA and EIP were predominantly due to the inability of these assays to detect low levels of GADAb in IDDM. To convert results to standard units, standard curves were constructed using duplicate dilutions of the anti-glutamic acid decarboxylase monoclonal antibody MICA 3 and serum from a patient with stiff-man syndrome (SMS). Curves could be derived in 28 assays using the MICA 3 serum and in 29 using the SMS serum. The mean coefficients of variation between assays for disease and control samples were 45% when results were converted to MICA units, 77% for SMS units, and 76% for SD scores.(ABSTRACT TRUNCATED AT 250 WORDS)

[Leukocytic procoagulant activity and chemotherapeutic drugs: the comparative effects of cisplatin and carboplatin on lympho-/monocytic procoagulant activity in vitro]

It is well known that a number of chemotherapeutic agents are able to induce procoagulating activity not only in neoplastic cells but also in normal, monocyte/macrophage cells, and some of them, including cisplatin, even increase procoagulating activity of the factor already expressed, providing a further example of the possible co-participation of chemotherapy in the onset of thrombotic complications in cancer patients. Carboplatin is an analogue of cisplatin but differs strikingly in terms of its collateral effects, in particular being less oto- and nephrotoxic. To the authors' knowledge there are no data regarding the possible effect of carboplatin on lympho/monocyte procoagulating activity. This study shows that not only platin but also carboplatin is able to increment the levels of lympho/monocyte procoagulating activity in vitro, with a dose-dependent effect, and to synergize with bacterial endotoxin in increasing this leukocyte activity, although the synergic effect is significantly greater in the case of carboplatin. The importance of these findings at a practical and clinical and clinical level still remains to be defined, in particular in the light of the different pharmacokinetic behaviour of these two chemotherapeutic agents and in the context of those neoplastic diseases for which cisplatin and carboplatin treatment is most frequently used.

[Leukocyte procoagulant activity and chemotherapeutic agents: comparison between the effects of adriamycin and epiadriamycin on the procoagulant lympho/monocytic activity in vitro]

It is well known that a number of antineoplastic agents are able to induce procoagulant cellular activity and tissue factor not only in neoplastic cells but also in normal, monocyte/macrophage cells, and some of them, including adriamycin, even increase procoagulating activity of the factor already expressed, providing a further example of the possible co-participation of chemotherapy in the onset of thrombotic complication in cancer patient. Epirubicin is an analogue of adriamycin but differs strikingly in terms of its collateral effect, in particular being less cardiotoxic. To the authors' knowledge there are no data regarding the possible effect of epirubicin on lympho/monocyte procoagulant activity. This study shows that not only adriamycin but also epirubicin is able to increment the level of lympho/monocyte procoagulant activity "in vitro", with a dose-dependent effect, and to synergize with bacterial endotoxin in increasing this leukocyte activity, although the effect is significantly greater in the case of adriamycin. The importance of these findings at practical and clinical level remains to be defined, in particular in the length of the different pharmacokinetic behavior of these two chemotherapeutic agents and in the context of those neoplastic diseases for which adriamycin and Epirubicin treatment is most frequently used.

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)

Autoantibodies to glutamic acid decarboxylase in palatal myoclonus and epilepsy

We report the presence of serum autoantibodies directed against glutamic acid decarboxylase in a patient with epilepsy and palatal myoclonus not associated with brain lesions. Glutamic acid decarboxylase antibody reactivity was dependent on the presence of carboxy-terminal amino acids, similar to that reported in patients with stiff-man syndrome. Marked reduction in the frequency of epileptic attacks and improvement in palatal myoclonus occurred when benzodiazepine was administered and phenytoin was gradually tapered. Testing for anti-glutamic acid decarboxylase antibodies may be indicated in patients with palatal myoclonus and with convulsive disorders refractory to therapy.

Sera from patients with IDDM and healthy individuals have antibodies to ICA69 on western blots but do not immunoprecipitate liquid phase antigen

ICA69 is a recently cloned pancreatic islet protein proposed as a potential target of autoimmunity in insulin dependent diabetes mellitus (IDDM). The aim of our study was to verify the relevance of ICA69 antibodies as markers of the disease. We measured antibodies to ICA69 in sera from newly-diagnosed IDDM patients, in age- and sex-matched normal controls, and in sera prior to the onset of IDDM (pre-IDDM). Human islet ICA69 was cloned and inserted into a bacterial expression vector and an in vitro transcription vector. Binding to affinity purified recombinant ICA69 on Western blots was found in 33/48 (68%) sera from newly-diagnosed IDDM patients and in 36/56 (64%) controls. No differences in band intensity were found between IDDM and controls. Using immunoprecipitation of 35S methionine labelled in vitro translated ICA69, none of 53 sera from newly diagnosed IDDM patients, 0 of 57 control sera and 1 of 24 pre-IDDM sera had detectable antibodies. We conclude that solid-phase assays are inappropriate for measurement of ICA69 antibodies as specific markers of IDDM and that antibodies to ICA69 are not detected by a liquid-phase immunoprecipitation assay. These data support neither a role for ICA69 as a relevant autoantigen in IDDM, nor a role for the measurement of antibodies to ICA69 in the prediction of IDDM.

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.

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)

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.

Low interleukin-2 receptor levels in serum of patients with insulin-dependent diabetes

Interleukin-2 receptors are released in the circulation in response to antigenic ro mitogenic stimulation of T-lymphocytes. Abnormal serum interleukin-2 receptor levels have been found in young children with type 1 diabetes and "prediabetes." We measured interleukin-2 receptor levels in 17 patients with newly diagnosed type 1 diabetes, 21 patients with long-standing type 1 diabetes, 19 patients with long-standing type 2 diabetes, 19 islet-cell antibody positive nondiabetic polyendocrine patients, 12 islet-cell antibody-positive first-degree relatives of patients with type 1 diabetes and compared the results to age- and sex-matched normal controls. We found significantly lower interleukin-2 receptor levels in patients with newly diagnosed and long-standing type 1 diabetes compared to normal controls (87 +/- 11 and 93 +/- 11 vs. 142 +/- 25 and 132 +/- 40 U/ml, P < 0.001 and P < 0.01). There were no significant differences in interleukin-2 receptor levels between prediabetic groups and normal controls or patients with long-standing type 1 or type 2 diabetes. There was no correlation between glycosylated hemoglobin, blood glucose levels, and interleukin-2 receptor in the groups with long-standing type 1 or type 2 diabetes. We conclude that patients with type 1 diabetes have low interleukin-2 receptor serum levels. This phenomenon is acquired close to disease onset and is unlikely to be an early markers of type 1 diabetes.

Slow metabolic deterioration towards diabetes in islet cell antibody positive patients with autoimmune polyendocrine disease

We studied metabolic progression to IDDM in a cohort of adults who are ICA-positive and have associated autoimmune endocrine disease or circulating organ-specific autoantibodies (the Polyendocrine Study). Of the 186 individuals recruited 27 developed overt diabetes after a median follow-up of 4.5 years (range 0.4-12). Of these, eight patients did not require insulin treatment until at least 6 months after clinical diagnosis, with an interval of 1.8 years (1.2-5.7). An IVGTT was performed in 38 subjects and 23 had sequential studies. Of the initial 38 subjects six developed diabetes and only three showed a loss of FPIR to glucose (below the first percentile of a normal control group) before clinical onset of the disease. An additional three subjects showed a loss of the FPIR, and all still have normal glucose tolerance after median follow-up of 28 months (22-95). A "whole" or "mixed" pattern of islet cell staining was found in five of the six patients who developed diabetes and antibodies against an islet 37 k-antigen were detectable in four patients, all of whom required insulin soon after diagnosis. A beta-cell "selective" ICA staining pattern was seen in 14 of 17 subjects who did not develop diabetes and the "mixed" pattern in only three. None of this group had detectable 37 k-antibodies. We conclude that metabolic deterioration is slow in polyendocrine patients, and that the IVGTT has less prognostic significance in this group than in first degree relatives of patients with IDDM.(ABSTRACT TRUNCATED AT 250 WORDS)

Can we really predict IDDM?

Risk of progression to IDDM has been assessed extensively in first-degree relatives of IDDM patients, and highly specific prediction is possible within a small subset of this population. Because approximately 90% of future cases will come from those who have no close relative with IDDM, prediction and intervention within the general population will become the main priority for the future. This review presents a decision tree analysis of risk of progression to IDDM, highlights the different prognosis of markers when applied to those with and without a family history of the disease, and proposes a strategy for disease prediction in the latter. Large collaborative studies in well-characterized populations will allow new predictive markers and models to be evaluated, and strategies of intervention to be tested with maximum efficiency and minimal delay.

Can islet cell antibodies predict IDDM in the general population?

OBJECTIVE

To evaluate the likely prognostic significance of ICAs in children with no family history of IDDM.

RESEARCH DESIGN AND METHODS

We examined the prevalence of ICAs in 2925 English schoolchildren aged 9-13 yr and in 274 age-matched siblings of children with diabetes from the same region, and we compared the estimated risk of progression to diabetes within 10 yr in the two groups.

RESULTS

ICAs were present at levels > or = 4 JDF U in 2.8% of schoolchildren and 6.6% of siblings and at > or = 20 JDF U in 0.8% of schoolchildren and 2.2% of siblings. Although ICAs are only 2-3 times more prevalent in siblings than schoolchildren, the estimated cumulative risk that siblings will progress to diabetes by age 21 is 13 times greater (2.8 vs. 0.21%).

CONCLUSIONS

ICAs are unexpectedly prevalent in English schoolchildren, but only a small minority, with this evidence of immune activation directed against islet cells, will progress to diabetes. Although ICAs alone have limited predictive value in the general population, combining two or more predictive tests in series could achieve a level of prediction equivalent to that now obtained in first-degree relatives.

Idiopathic dilated cardiomyopathy: lack of association between circulating organ-specific cardiac antibodies and HLA-DR antigens

Organ-specific cardiac antibodies are serological markers of autoimmunity in dilated cardiomyopathy (DCM). HLA-DR4 and possibly DR5 are immunogenetic markers of susceptibility in DCM, but it is not known whether they are associated with autoantibody production. We studied the frequency of HLA-DR antigens and the presence of organ-specific cardiac antibodies in 80 DCM Caucasian patients from Northern Italy. HLA-DR typing was performed by serology; 289 healthy blood donors from the same region were tested as controls. HLA-DR frequencies in DCM were also compared with VIII International Workshop control data for Italy. Cardiac antibodies were detected by indirect immunofluorescence on human heart. Skeletal muscle was used to identify cross-reacting antibodies. The prevalence of cardiac antibodies in DCM was: organ-specific 34% and skeletal muscle cross-reactive 30%. The previously reported positive association between DCM and HLA-DR4 was confirmed using either the controls from the same region (21.25% vs 10.73% p = 0.02, relative risk = 2.30) or from all of Italy (21.25% vs 12.3%, p = 0.03). HLA-DR5 frequency was slightly but not significantly higher in DCM than in controls from the same region (46.25% vs 31.49% p = 0.02, relative risk of 1.87, p corrected = NS) or from all of Italy (46.25% vs 35.8% p = NS). HLA-DR3 frequency was lower in DCM than in controls from the same region (12.50% vs 29.41% p = 0.003, relative risk of 0.36, p corrected = 0.03). This negative association was not confirmed using the control data from the whole of Italy (12.50% vs 16.5% p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Distinct cytoplasmic islet cell antibodies with different risks for type 1 (insulin-dependent) diabetes mellitus

The cytoplasmic islet cell antibody patterns of sera from islet cell antibody positive non-diabetic and diabetic endocrine autoimmune patients, and newly-diagnosed Type 1 (insulin-dependent) diabetic patients were characterised using four layer immunofluorescence with monoclonal anti-proinsulin or anti-glucagon antibodies. Two distinct islet cell antibody types were identified. One gave a diffuse cytoplasmic staining in both Beta and Alpha cells ('whole' islet pattern), and was not affected by pre-incubation with rat brain homogenate. The other had a granular appearance with staining restricted predominantly to Beta cells ('selective' islet pattern) and was completely inhibited by pre-incubation with rat brain homogenate. Some sera appeared to have a 'mixed' islet pattern, in which glucagon-positive cells gave a weaker cytoplasmic staining than proinsulin-positive cells. The granular 'selective' pattern was found in sera from 19 (79%) of 24 non-diabetic endocrine autoimmune patients, in two (22%) endocrine autoimmune patients who developed Type 1 diabetes (p less than 0.0001 vs non-diabetic endocrine autoimmune patients), and in none of 19 newly-diagnosed diabetic patients. The 'whole' islet pattern was found only in sera from patients who had, or who subsequently progressed to, Type 1 diabetes. This study has identified a novel islet cell antibody specificity and demonstrates that in islet cell antibody positive endocrine autoimmune patients, only islet cell antibodies which stain both Beta and Alpha cells are associated with progression to Type 1 diabetes.

[Idiopathic dilated cardiomyopathy: a persistent viral infection or an organ-specific autoimmune disease? The trial of 2 major pathogenetic hypotheses]

Aetiology and pathogenesis of idiopathic dilated cardiomyopathy (DCM) are uncertain. The two major pathogenetic hypotheses are: 1) autoimmunity; 2) persistent viral infection. Indirect evidence for virus association comes from the finding of raised titres of antibody to coxsackievirus in DCM, but infectious virus has never been isolated in myocardium from DCM patients. Bowles et al. using the slot-blotting technique reported that enteroviral RNA was commonly detectable in the myocardium of patients with myocarditis (53%) and with DCM (52%). Other groups using this as well as more refined hybridization techniques have failed to confirm such a high prevalence. Detection of enteroviral genomic RNA in cardiac tissue does not, however, imply active infection or pathogenicity. Thus the mechanisms of chronic myocardial damage in the absence of whole competent infectious virus remain uncertain. The other major pathogenetic hypothesis in DCM involves autoimmune mediated damage to myocytes. Circulating organ specific autoantibodies have been reported in a quarter of a group of patients with idiopathic DCM. This suggests that there may be autoimmune mechanisms operating at least in this subset of patients, but the exact relation of these antibodies to the pathogenesis and prognosis needs to be defined. The abnormal expression of major histocompatibility complex class II antigens on cardiac microvascular endothelium in endomyocardial biopsy tissue from DCM patients, and the reported association with HLA-DR4 phenotype lend further support to the autoimmune hypothesis. The viral and the autoimmune hypothesis in chronic myocarditis and in DCM are not mutually exclusive. In experimentally murine virus-induced myocarditis infectious virus can no longer be recovered from the myocardium after two weeks, although nucleic acid sequences of the viral genome are still detectable. The development of chronic inflammation takes place only in mice with a predisposing genetic background. Chronic myocyte damage is associated with the production of circulating heart-specific autoantibodies and autoreactive lymphocytes. In this animal model chronic myocarditis appears to be a virus-triggered or precipitated autoimmune disease, rather than a persistent viral infection with tissue damage due to active virus synthesis and replication. A similar transition from acute myocarditis into DCM may occur in man.

Early T-cell defects in pre-type 1 diabetes

Alterations of lymphocyte subsets have been recently reported in pre-type 1 diabetes but the relation with other immunological markers, in particular islet cell antibodies (ICA), is still unknown. In the present study, we have investigated prospectively changes of lymphocyte subsets in 86 first-degree relatives of patients affected by type 1 diabetes and correlated such modifications with ICA titres. Among individuals with persistent ICA, 8 had ICA titres of more than 20 JDF units, 14 had ICA titres between 5 and 20 JDF units and 64 had ICA titres between 0 and 5 JDF units. First-degree relatives with ICA titres of more than 20 JDF units had significantly decreased proportions of CD3 cells. This reduction was predominantly in the CD4 subset, giving rise to a decreased CD4/CD8 lymphocyte ratio. Those with ICA titres between 5 and 20 JDF units showed abnormalities in both CD3 and CD4 lymphocytes, but not in CD4/CD8 lymphocyte ratio. Further characterization of the CD4 cell subset was performed using three other monoclonal antibodies, CD45RO (UCHL1), CD45RA and CD29, phenotyping memory T-cells, the inducer cells of suppressor function and helper-inducer cells, respectively. The proportions of total CD45RO and CD45RA were not significantly different among first-degree relative with distinct ICA titres in a cross-sectional study, whereas a trend towards a reduced proportion of CD4/CD45RA cells was observed. The longitudinal study demonstrated that individuals potentially susceptible to the development of type 1 diabetes and who possess high titres of ICA have impairment of CD4/CD8 lymphocyte ratio, mainly due to a reduction in the CD4 subset.(ABSTRACT TRUNCATED AT 250 WORDS)

Novel considerations on the antibody/autoantigen system in type I (insulin-dependent) diabetes mellitus

Insulin dependent diabetes (IDDM) has an autoimmune pathogenesis. Included is the presence of antibodies to pancreatic islet cells. The first identified were islet cell antibodies (ICA), detected by indirect immunofluorescence, and which react with all cells within islets. Importantly, the autoantibodies are found several years prior to disease and although a pathogenic role for the autoantibodies is unclear, they have become useful markers of prediabetes. A number of studies of twins discordant for IDDM and of first degree relatives of IDDM patients have established that there is an increased risk for disease in individuals who have ICA, especially when ICA levels are high. This high predictive value of ICA decreases in the general population where the incidence of IDDM is lower than in first degree relatives, and both ICA and the disease risk associated with ICA, appear to be influenced by a genetic susceptibility. This has been sustained in a study of patients with endocrine autoimmunity and ICA (Polyendocrine Study) where the predictive value of very high levels of ICA is less than 50% in patients without a first degree relative with IDDM. Hence, there remain a substantial number of patients with ICA who do not develop disease. From these patients, it was demonstrated that ICA include at least two distinct specificities, one of which is beta cell specific and is not associated with a high risk for IDDM.(ABSTRACT TRUNCATED AT 250 WORDS)