Peptides Derived From Insulin Granule Proteins Are Targeted by CD8+ T Cells Across MHC Class I Restrictions in Humans and NOD Mice

The antigenic peptides processed by β-cells and presented through surface HLA class I molecules are poorly characterized. Each HLA variant (e.g., the most common being HLA-A2 and HLA-A3) carries some peptide-binding specificity. Hence, features that, despite these specificities, remain shared across variants may reveal factors favoring β-cell immunogenicity. Building on our previous description of the HLA-A2/A3 peptidome of β-cells, we analyzed the HLA-A3-restricted peptides targeted by circulating CD8⁺ T cells. Several peptides were recognized by CD8⁺ T cells within a narrow frequency (1-50/10⁶), which was similar in donors with and without type 1 diabetes and harbored variable effector/memory fractions. These epitopes could be classified as conventional peptides or neoepitopes, generated either via peptide cis-splicing or mRNA splicing (e.g., secretogranin-5 [SCG5]-009). As reported for HLA-A2-restricted peptides, several epitopes originated from β-cell granule proteins (e.g., SCG3, SCG5, and urocortin-3). Similarly, H-2K^d-restricted CD8⁺ T cells recognizing the murine orthologs of SCG5, urocortin-3, and proconvertase-2 infiltrated the islets of NOD mice and transferred diabetes into NOD/scid recipients. The finding of granule proteins targeted in both humans and NOD mice supports their disease relevance and identifies the insulin granule as a rich source of epitopes, possibly reflecting its impaired processing in type 1 diabetes.

Islet-reactive CD8+ T cell frequencies in the pancreas, but not in blood, distinguish type 1 diabetic patients from healthy donors

The human leukocyte antigen-A2 (HLA-A2)-restricted zinc transporter 8_186-194 (ZnT8_186-194) and other islet epitopes elicit interferon-γ secretion by CD8⁺ T cells preferentially in type 1 diabetes (T1D) patients compared with controls. We show that clonal ZnT8_186-194-reactive CD8⁺ T cells express private T cell receptors and display equivalent functional properties in T1D and healthy individuals. Ex vivo analyses further revealed that CD8⁺ T cells reactive to ZnT8_186-194 and other islet epitopes circulate at similar frequencies and exhibit a predominantly naïve phenotype in age-matched T1D and healthy donors. Higher frequencies of ZnT8_186-194-reactive CD8⁺ T cells with a more antigen-experienced phenotype were detected in children versus adults, irrespective of disease status. Moreover, some ZnT8_186-194-reactive CD8⁺ T cell clonotypes were found to cross-recognize a Bacteroides stercoris mimotope. Whereas ZnT8 was poorly expressed in thymic medullary epithelial cells, variable thymic expression levels of islet antigens did not modulate the peripheral frequency of their cognate CD8⁺ T cells. In contrast, ZnT8_186-194-reactive cells were enriched in the pancreata of T1D patients versus nondiabetic and type 2 diabetic individuals. Thus, islet-reactive CD8⁺ T cells circulate in most individuals but home to the pancreas preferentially in T1D patients. We conclude that the activation of this common islet-reactive T cell repertoire and progression to T1D likely require defective peripheral immunoregulation and/or a proinflammatory islet microenvironment.

Conventional and Neo-antigenic Peptides Presented by β Cells Are Targeted by Circulating Naïve CD8+ T Cells in Type 1 Diabetic and Healthy Donors

Although CD8⁺ T-cell-mediated autoimmune β cell destruction occurs in type 1 diabetes (T1D), the target epitopes processed and presented by β cells are unknown. To identify them, we combined peptidomics and transcriptomics strategies. Inflammatory cytokines increased peptide presentation in vitro, paralleling upregulation of human leukocyte antigen (HLA) class I expression. Peptide sources featured several insulin granule proteins and all known β cell antigens, barring islet-specific glucose-6-phosphatase catalytic subunit-related protein. Preproinsulin yielded HLA-A2-restricted epitopes previously described. Secretogranin V and its mRNA splice isoform SCG5-009, proconvertase-2, urocortin-3, the insulin gene enhancer protein ISL-1, and an islet amyloid polypeptide transpeptidation product emerged as antigens processed into HLA-A2-restricted epitopes, which, as those already described, were recognized by circulating naive CD8⁺ T cells in T1D and healthy donors and by pancreas-infiltrating cells in T1D donors. This peptidome opens new avenues to understand antigen processing by β cells and for the development of T cell biomarkers and tolerogenic vaccination strategies.

Erosion of the chronic myeloid leukaemia stem cell pool by PPARγ agonists

Whether cancer is maintained by a small number of stem cells or is composed of proliferating cells with approximate phenotypic equivalency is a central question in cancer biology. In the stem cell hypothesis, relapse after treatment may occur by failure to eradicate cancer stem cells. Chronic myeloid leukaemia (CML) is quintessential to this hypothesis. CML is a myeloproliferative disorder that results from dysregulated tyrosine kinase activity of the fusion oncoprotein BCR-ABL. During the chronic phase, this sole genetic abnormality (chromosomal translocation Ph(+): t(9;22)(q34;q11)) at the stem cell level causes increased proliferation of myeloid cells without loss of their capacity to differentiate. Without treatment, most patients progress to the blast phase when additional oncogenic mutations result in a fatal acute leukaemia made of proliferating immature cells. Imatinib mesylate and other tyrosine kinase inhibitors (TKIs) that target the kinase activity of BCR-ABL have improved patient survival markedly. However, fewer than 10% of patients reach the stage of complete molecular response (CMR), defined as the point when BCR-ABL transcripts become undetectable in blood cells. Failure to reach CMR results from the inability of TKIs to eradicate quiescent CML leukaemia stem cells (LSCs). Here we show that the residual CML LSC pool can be gradually purged by the glitazones, antidiabetic drugs that are agonists of peroxisome proliferator-activated receptor-γ (PPARγ). We found that activation of PPARγ by the glitazones decreases expression of STAT5 and its downstream targets HIF2α and CITED2, which are key guardians of the quiescence and stemness of CML LSCs. When pioglitazone was given temporarily to three CML patients in chronic residual disease in spite of continuous treatment with imatinib, all of them achieved sustained CMR, up to 4.7 years after withdrawal of pioglitazone. This suggests that clinically relevant cancer eradication may become a generally attainable goal by combination therapy that erodes the cancer stem cell pool.

[Cushing's syndrome during pregnancy]

The rare association of Cushing's syndrome and pregnancy is explained by the amenorrhea and sterility inherent to the syndrome. In the literature, 125 cases have been reported: 30 cases of early diagnosis and 95 others diagnosed in the second half of pregnancy.

AT THE START OF PREGNANCY

When hypercorticism exists before pregnancy it is hardly secretory. Its diagnosis, at an early stage, is not hindered by the hormone modifications of pregnancy. Its aetiological treatment raises the problem of the compatibility in pursuing the latter.

IN THE SECOND HALF OF PREGNANCY

The positive and aetiological diagnoses of Cushing's syndrome are difficult and its prevalence may therefore be underestimated. The evocative clinical signs are unspecific: excessive weight gain, hypertension of pregnancy and gestational diabetes. The 24-hour free hypercortisoluria and the absence of dexamethasone inhibition are of little diagnostic value after the 14th week of amenorrhea. The positive diagnosis therefore relies essentially on the abolition of the circadian rhythm of cortisol. The biological hyperandrogenia commonly observed is not discriminating. Adrenal aetiologies are frequent. Imaging must be performed to eliminate an adrenocortical tumor.

PROGNOSIS

The maternal prognosis depends on the hypertension, preeclampsia, diabetes and the complications of Cushing's syndrome. It depends on the activity of the hypercorticism and its early aetiological treatment, which must not be delayed after pregnancy. The foetal prognosis depends on the maternal prognosis. It is represented by preterm delivery, hypotrophy and death of the foetus in utero. The therapeutic management must be symptomatic and aetiologic, maternal and obstetrical.

From guidelines to hospital practice: reducing inappropriate ordering of thyroid hormone and antibody tests

OBJECTIVE

Because of major technical improvements and conscious care about cost effectiveness, limiting the inadequate use of thyroid biological tests appears to be a major issue.

DESIGN

To (i) estimate the ordering prevalence of each thyroid test, (ii) assess the prevalence of relevant thyroid tests, and (iii) evaluate the impact of expressing justification for tests during a 2-month intervention period on these prevalences.

METHODS

During a prospective 2-month survey (June-July 1997), all the request forms were divided into four groups of prescription: (1) investigation of thyroid function, (2) taking drugs affecting the thyroid, (3) monitoring of nodule and cancer, and (4) investigation of thyroid autoimmunity. Their appropriateness was thus determined according to consensus in our hospital and previously published recommendations. Results were compared with those of retrospective similar 2-month periods in 1996 and 1998. Combinations of thyroid function tests and thyroid antibodies were analyzed during the 1996, 1997 and 1998 periods.

RESULTS

The overall estimated rate of appropriate ordering between 1996 and 1997 increased from 42.5% to 72.4% (P<10(-4)), with a significant improvement in each group of main diagnosis referral, except in group 3 where suitability was always over 85%. However, in group 4, appropriateness remained low (36%). Combinations of thyroid tests revealed an increase in single TSH order forms and single autoantibodies to thyroperoxidase (TPOAb) ones, while TSH+free thyroxine+free tri-iodothyronine and TPOAb+ autoantibodies to thyroglobulin ones decreased significantly. Interestingly, all these changes were maintained 1 year later (June-July 1998) even though physicians were not aware of this new study.

CONCLUSIONS

Persistent change in medical practice was thus assessed.

Sporadic medullary microcarcinoma of the thyroid: a retrospective analysis of eighty cases

Clinical characteristics and prognosis of 80 patients (53 women and 27 men) with sporadic medullary thyroid carcinomas (MTC), less than 1 cm in size (micro-MTC), operated on between 1971 and 1996 are reported (73 total and 7 partial thyroidectomies). These patients, obtained from a national database of 899 patients with MTC, were compared with 357 cases of sporadic MTC greater than 1 cm and 149 subjects with familial MTC less than 1 cm (familial micro-MTC). Median age at surgery was 52.5 years, a distribution similar to larger sporadic MTC. Micro-MTC was identified due to elevated calcitonin (47.5%), clinically identified lymph node (10.0%), distant metastases (6.3%) or pathologic finding at surgery (36.2%). Diarrhea and/or flushing were observed in 6 patients including 4 with clinically identified lymph node. Among patients who had lymph node dissection at surgery (68.8%), lymph node involvement with tumor was observed in 30.9%, and was significantly more frequent in multifocal (7/11) than in unifocal micro-MTC (p < 0.03). All sporadic micro-MTC were unilateral. Survival rate was 93.9% +/- 4.4% (SE) at 10 years, greater than that observed in sporadic macro-MTC (p = 0.04). Normal postoperative basal calcitonin (CT) was obtained in 71.1% of micro-MTC patients versus 33.6% in sporadic macro-MTC (p < 0.01). Sporadic micro-MTC is much more frequent than expected, 15% of MTC in our series. Although specific survival rate and percentage of biological cure in micro-MTC are significantly better than for larger tumors, the frequency of lymph node involvement, however, justifies an aggressive surgical approach including total thyroidectomy and bilateral central lymph node dissection.

[Peripheral adrenal insufficiency in AIDS]

BACKGROUND

Lesions of adrenal glands are common findings at autopsy of patients with acquired immunodeficiency syndrome (AIDS). In contrast the diagnosis of symptomatic adrenal insufficiency is rarely established during the lifetime of these patients.

PATIENTS

We report four new cases and review the literature. All four patients had full blown AIDS with a mean CD4 cell count of 19 mu/L. One or more opportunistic disease was present at the time of diagnostic: cytomegalovirus retinitis in two cases, disseminated Mycobacterium avium infection in two, Kaposi's sarcoma in two and Candida esophagitis in one.

RESULTS

The clinical presentation constantly included fatigue, weight loss, severe orthostatic hypotension and gastrointestinal disturbances. Cutaneous hyperpigmentation was present in three cases. In most cases biological abnormalities were typical, such as hyponatremia, urinary Na/K ratio > or = 1, and hyperkalemia. Serum cortisol levels were within the range of normal in three cases but response to the cosyntropin challenge was typically impaired in all cases. Clinical and biological manifestations returned to normal in 1 to 3 weeks after initiation of therapy with cortisol, associated to fludrocortisone in three cases. However, 13 months after diagnosis, three patients were dead.

CONCLUSION

Usually asymptomatic, diagnostic of symptomatic adrenal insufficiency must be suspected even when clinical presentation is atypical because rapid efficiency of hormonal treatment.

Short- and long-term follow-up of thyroid dysfunction after allogeneic bone marrow transplantation without the use of preparative total body irradiation

We studied the incidence and potential prognostic value of thyroid abnormalities after allogeneic bone marrow transplantation (BMT) without total body irradiation (TBI) conditioning. 77 consecutive patients who received a chemotherapy-alone-based conditioning regimen pretransplant were included. Free serum thyroxine (FT4), free serum triiodothyronine (FT3) and serum thyrotropin (TSH) levels were assayed before and 3 and 14 months after BMT. Patients were classified in three categories: normal thyroid profile if FT3 and FT4 were within the normal range and TSH was normal or low, peripheral thyroid insufficiency (PTI) if TSH was >4 mIU/l, or an 'euthyroid sick syndrome' (ETS) if FT3 and/or FT4 were low and TSH was normal or low. The incidence of thyroid dysfunction at 3 months was 57%, and 29% at 14 months. This was mostly due to the occurrence of ETS which was more frequent at 3 months (48%, 29/61) than at 14 months (19%, 9/48). Furthermore, at 3 months, survival was significantly lower in the ETS group (34.5%) than in the euthyroid group (96.2%), or in the PTI group (83.3%) (P < 0.0001). PTI was observed even in the absence of TBI in 11 patients (14%) and was equally distributed at 3 months (n = 6) and 14 months (n = 5). In conclusion, thyroid dysfunction is not a rare complication even without pretransplant TBI conditioning regimen. Hypothyroidism prevalence was 10%, and ETS, which was more frequently observed, displayed a dismal predictive value at 3 months.

Are the implications of the Diabetes Control and Complications Trial (DCCT) feasible in daily clinical practice?

The Diabetes Control and Complications Trial was conducted in heavily-equipped centres on a selected and motivated patient cohort. The aim of the present study was to evaluate at one-year follow-up the results of intensive insulin therapy in patients with insulin-dependent diabetes mellitus attending a department of diabetology. From October 1, 1993, to December 31, 1994, all our hospitalised patients under 55 years of age with HbA1c levels above 8% and receiving 2 daily insulin injections were offered the opportunity to shift to 3 daily injections (short-acting insulin in the morning and at midday, and a mixture of short-acting and intermediate insulin in the evening). Patients were instructed to increase blood glucose self-monitoring and to see their diabetologist more often (once every two months). Five patients refused and 45 accepted this proposal: 22 women and 23 men (mean age 31.8 +/- 10.9 yr), BMI 23.5 +/- 2.9 kg/m2, duration of diabetes 12.8 +/- 10.1 yr, HbA1c 10.0 +/- 2.0%. Five patients were lost to follow-up, 2 asked to have their medical file transferred, 3 returned to 2 daily injections, and 5 consulted only once during the year of follow-up. For the 29 patients seen after one-year follow-up, the decrease in HbA1c levels from 10.0 +/- 1.9% to 9.5 +/- 1.8% was not statistically significant. Sixteen patients complained of increased occurrence of hypoglycaemia (3 comas). In routine clinical practice, the prescription of intensive insulin therapy to non-selected insulin-dependent diabetic patients can be associated with a high number of patients lost to follow-up (17% in our study). An increase in the number of daily insulin injections will improve glycaemic control only if self-monitoring and medical surveillance are also intensified. However, many long-term poorly-controlled insulin-dependent diabetic patients are reluctant to comply with these recommendations.

Genetic mapping of a susceptibility locus for insulin-dependent diabetes mellitus on chromosome 11q

Loci in the major histocompatibility complex (MHC) on chromosome 6 and the insulin (INS) region on chromosome 11 have been implicated in susceptibility to insulin-dependent diabetes mellitus (IDDM) through candidate gene investigations, but they may account for less than 50% of genetic risk for the disease. Genome-wide linkage studies have led to localization of more than 10 susceptibility loci for insulin-dependent diabetes in the non-obese diabetic (NOD) mouse and the BB rat. Similar studies are now possible in humans through the development of dense genetic maps of highly informative microsatellite loci obtained using polymerase chain reaction analysis. We have applied microsatellite markers from recent Généthon maps, and other highly informative markers, in a genome-wide linkage study in IDDM. Here we report evidence for the localization of a previously undetected susceptibility locus for IDDM in the region of the FGF3 gene on chromosome 11q. Our results shows the potential of genome-wide linkage studies to detect susceptibility loci in IDDM and other multifactorial disorders.

Pseudotumoral lymphocytic hypophysitis successfully treated by corticosteroid alone: first case report

We report the first case of pseudotumoral lymphocytic hypophysitis successfully treated by corticosteroids without surgery. A 27-year-old woman had been monitored for chronic headache 13 months after giving birth, associated with amenorrhea and galactorrhea. Cranial magnetic resonance imaging revealed a markedly enlarged pituitary gland with a suprasellar extension; the only biochemical abnormality was a mild hyperprolactinemia. Because of a putative diagnosis of prolactinoma, bromocriptine was prescribed at a dose of 5 mg daily, soon followed by the transitory appearance of menstruation. Two years later, panhypopituitarism was present and was revealed by acute adrenal insufficiency. Magnetic resonance imaging revealed that the pituitary mass was the same as previously described, but hormonal investigation showed evidence of complete hypopituitarism and no hyperprolactinemia. Nuclear antibodies were negative as well as other autoantibodies. Human leukocyte antigen serological Class II typing was DR3/DR4. Lymphocytic hypophysitis was then suspected; in the absence of visual complication and because this patient refused surgery, corticosteroids were attempted at a daily dose of 60 mg of prednisone for 3 months, progressively decreased for the next 6 months. Under this treatment, a gradual recovery of all pituitary hormones was observed and magnetic resonance imaging showed a reduction of two-thirds in pituitary mass. Five months after the end of corticoid treatment, our patient relapsed with panhypopituitarism and an increase of pituitary volume. She underwent steroid treatment, and a biopsy was performed and confirmed the diagnosis of autoimmune hypophysitis.(ABSTRACT TRUNCATED AT 250 WORDS)

Susceptibility to insulin dependent diabetes mellitus maps to a 4.1 kb segment of DNA spanning the insulin gene and associated VNTR

Recent studies have demonstrated that a locus at 11p15.5 confers susceptibility to insulin dependent diabetes mellitus (IDDM). This locus has been shown to lie within a 19 kb region. We present a detailed sequence comparison of the predominant haplotypes found in this region in a population of French Caucasian IDDM patients and controls. Identification of polymorphisms both associated and unassociated with IDDM has allowed us to define further the region of association to 4.1 kb. Ten polymorphisms within this region are in strong linkage disequilibrium with each other and extend across the insulin gene locus and the variable number tandem repeat (VNTR) situated immediately 5' to the insulin gene. These represent a set of candidate disease polymorphisms one or more of which may account for the susceptibility to IDDM.

Genetic determinants of diastolic and pulse pressure map to different loci in Lyon hypertensive rats

Several genetic loci involved in blood pressure regulation have recently been localized in experimental models of hypertension, but the manner in which they influence blood pressure remains unknown. Here, we report a study of the Lyon hypertensive rat strain showing that different loci are involved in the regulation of steady-state (diastolic pressure) and pulsatile (systolic-diastolic, or pulse pressure) components of blood pressure. Significant linkage was established between diastolic blood pressure and a microsatellite marker of the renin gene (REN) on rat chromosome 13, and between pulse pressure and the carboxypeptidase B gene (CPB) on chromosome 2. These findings show that two independent loci influence different haemodynamic components of blood pressure, and that pulse pressure has a specific genetic determination.

The HLA-DRB1*0405 haplotype is most strongly associated with IDDM in Algerians

Insulin-dependent diabetes mellitus (IDDM) in Caucasians is strongly associated with HLA-DR3-DQ2 and DR4-DQ8. In order to investigate the HLA class II associations with IDDM in Algerians, we have used polymerase chain reaction (PCR) and sequence specific oligonucleotide analysis (SSO) to identify DQA1, DQB1, and DRB1 alleles, haplotypes and genotypes in 50 unrelated IDDM patients and 46 controls from a homogeneous population in Western Algeria. Both DRB1*0301-DQA1*0501-DQB1*0201 (DR3-DQ2) and DRB1*04-DQA1*0301-DQB1*0302 (DR4-DQ8) haplotypes were found at increased frequencies among the patients compared to controls (45% vs. 13%, RR = 5.5, Pc < 10(-5) and 37% vs. 4%, RR = 12.9, Pc < 10(-4), respectively). Among the latter, in contrast to other Caucasian populations, only DRB1*0405-DQA1*0301-DQB1*0302 was significantly increased in the Algerian patients (25% vs. 1% in controls, RR = 30.3, Pc < 10(-3). Accordingly, the highest risk of disease was observed in DRB1*0301-DQA1*0501-DQB1*0201/DRB1*0405-DQA1+ ++*0301-DQB1*0302 heterozygotes (34% in patients vs. 0% in controls; RR = 49; Pc < 10(-3). This observation and its comparison with DR-DQ haplotypes in other ethnic groups suggest that the DRB1*0405 allele which encodes an Asp57-negative beta chain may contribute to IDDM susceptibility in a similar way as Asp57-negative DQ beta chains.

HLA DQA1 and DQB1 study in Algerian type 1 diabetes families

The distribution of HLA class II alleles associated with insulin-dependent diabetes mellitus (Type 1) in the Algerian population is poorly known. We have typed 36 Algerian Type 1 diabetic probands and their families using DQA1 and DQB1 oligonucleotide probes. Fifty-nine parental haplotypes non transmitted to diabetic offspring served as controls. The frequencies of DQA1 and DQB1 alleles and haplotypes and their associations with Type 1 diabetes were, except minor differences, similar to those reported in French. Susceptibility DQA1 (Arg52+) and DQB1 (Asp57-) alleles were significantly increased among patients versus controls (90% vs 53%, RR = 8.4, p < 10(-6), and 94% vs 64%, RR = 9.4, p < 10(-5), respectively). 85% of Type 1 diabetics versus 34% of control haplotypes were either DR3DQw2 or DR4DQw8 susceptibility haplotypes (DQA1 Arg52+, DQB1 Asp57-) (RR = 10.8, p < 10(-7). 75% of the probands vs 14% of the controls (RR = 18, p < 10(-5)) and 73% of affected siblings versus 24% of unaffected siblings (RR = 8.4, p < 0.02) possessed a genotype composed of these two susceptibility haplotypes in the homozygous or heterozygous state. 42% of the probands were DR3DQw2/DR4DQw8, corresponding to Hardy-Weinberg expectations. The lack of excess of heterozygotes could be due to the consanguine families in this sample, as among the patients with consanguine parents the frequency of DR3, 4 heterozygotes was lower (27% vs 48% in non-consanguine patients, NS) and that of DR3 homozygotes increased (45% vs 12%, respectively, p < 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

The role of genetic predisposition to type I (insulin-dependent) diabetes mellitus

The aetiology of insulin-dependent diabetes (IDDM) involves genetic predisposition, a major component of which has been mapped in the HLA complex, near to or identical with genes encoding class II molecules. In Caucasian populations IDDM is strongly associated with the serologically defined HLA-DR3 and DR4 antigens, which are widely recognised as markers of susceptibility. The particularly high risk of DR3/DR4 heterozygotes suggests that susceptibility is determined by two genes acting synergistically. The development of recombinant DNA technology has allowed a finer description of the class II region and provided evidence that DQ rather than DR determinants may primarily influence IDDM susceptibility. The search for specific structural changes of the DQA and DQB genes has shown that susceptibility correlates with the absence of aspartic acid at position 57 on the DQ beta chain (DQ beta 57 Asp--) and/or the presence of arginine at position 52 on the DQ alpha chain (DQ alpha 52 Arg+). In Caucasians the formation of a putative DQ susceptibility molecule (DQ alpha 52 Arg+, DQ beta 57 Asp-) accounts best for the disease associations when transcomplementation molecules consisting of DQ alpha and beta chains encoded by different haplotypes are postulated to explain the excess risk of heterozygotes. The HLA-IDDM associations in the Japanese, however, are not explained by this model. These and other unresolved questions indicate that other residues of the DQ alpha and beta chains or other class II molecules (DR beta chains), as well as non-MHC genes, may also contribute to the susceptibility.

[New data concerning the etiology of insulin-dependent diabetes]

The mechanism of pancreatic beta-cell destruction in type I (insulin-dependent) diabetes mellitus (IDDM) involves autoimmune events directed against these cells. Anti-beta-cell autoimmunity occurs in genetically predisposed individuals and may precede clinical manifestations of IDDM by several years. Markers for beta-cell autoimmunity, especially islet-cell antibodies, are being used with increasing reliability both for detection of IDDM and for evaluating the risk of development of the disease. HLA alleles associated with IDDM include DR3 and DR4, with the risk of IDDM being especially high in individuals with the heterozygous combination DR3/DR4. Recent advances in molecular biology have resulted in more accurate identification of genetic variants and even of amino acid sequences associated with IDDM. These markers can be used to identify patients with genetic susceptibility to the disease. The mechanism of action of genes associated with IDDM is as yet unknown but probably involves the receptor function of HLA molecules for antigens during immune responses.