Immunogenetic heterogeneity in type I (insulin-dependent) diabetes among the Tunisian population. HLA-DR antigens and organ-specific autoantibodies (family study)

HLA class II alleles susceptibility markers of type 1 diabetes fail to specify phenotypes of ketosis-prone diabetes in adult Tunisian patients

We aimed to characterize the different subgroups of ketosis-prone diabetes (KPD) in a sample of Tunisian patients using the Aβ scheme based on the presence or absence of β-cell autoantibodies (A+ or A-) and β-cell functional reserve (β+ or β-) and we investigated whether HLA class II alleles could contribute to distinct KPD phenotypes. We enrolled 43 adult patients with a first episode of ketosis. For all patients we evaluated clinical parameters, β-cell autoimmunity, β-cell function and HLA class II alleles. Frequency distribution of the 4 subgroups was 23.3% A+β-, 23.3% A-β-, 11.6% A+β+ and 41.9% A-β+. Patients from the group A+β- were significantly younger than those from the group A-β- (P = .002). HLA susceptibility markers were significantly more frequent in patients with autoantibodies (P = .003). These patients also had resistance alleles but they were more frequent in A+β+ than A+β- patients (P = .04). Insulin requirement was not associated to the presence or the absence of HLA susceptibility markers. HLA class II alleles associated with susceptibility to autoimmune diabetes have not allowed us to further define Tunisian KPD groups. However, high prevalence of HLA resistance alleles in our patients may reflect a particular genetic background of Tunisian KPD population.

Spectrum of Autoantibodies in Tunisian Adult Type 1 Diabetes Mellitus

As an autoimmune disease, type 1 diabetes mellitus (T1DM) is characterized by the presence of several autoantibodies. The aim of this study was to examine a broad spectrum of antibodies in Tunisian adult T1DM and to compare their prevalence with a healthy control group. Two hundred sixty-one diabetics and 100 healthy blood donors were enrolled in this study. Indirect immunofluorescence was performed for the detection of islet cell, antiendomysial, antinuclear, antimitochondrial, antismooth muscle, antireticulin, and antikeratin antibodies. Enzyme-linked immunosorbent assay was used for measuring anticardiolipin, antigliadin, antitransglutaminase, and antithyroperoxidase antibodies. Latex agglutination was used for the detection of rheumatoid factors. As expected, islet cell antibodies were the most frequent (33.7%). Antigliadin, antithyroperoxidase, and antikeratin antibodies were relatively frequent (18%, 15.3%, and 10.3%, respectively) and were statistically more prevalent in diabetics than in controls. There was no correlation between diabetes duration and any autoantibody, except for islet cell antibodies that were more frequent at the onset of diabetes. Several autoantibodies nonspecific of diabetes are frequent in diabetic patients, which may be associated with or predictors of some autoimmune diseases, and can also reflect a special profile of autoimmunity in diabetics in comparison to healthy controls.

[Susceptibility markers in Tunisian first-degree relatives of patients with type 1 diabetes]

To identify the profile of anti-pancreas autoantibodies and elucidate the HLA DRB1, DQB1 polymorphism in Tunisian first-degree relatives of patients with type 1 diabetes, we recruited 96 relatives from 21 families with at least one diabetic child. Islet cell antibodies (ICA) were detected by immunofluorescence on monkey pancreas; glutamate decarboxylase (GADA), IA2 (IA2-A) and insulin (IAA) antibodies were measured by RIA. HLA class II DRB1 and DQB1 alleles were typed by PCR-SSP. ICA, GADA, IA2-A and IAA were found in respectively 11.5, 4.2, 5.2 and 8.3% of relatives. Twenty-two out of 96 had at least one antibody and 20 out of these 22 had a susceptibility allele (DRB1*03, DRB1*04, DQB1*02 or DQB1*0302) with or without protective allele (DRB1*11, DRB1*13, DRB1*15 or DQB1*06). All of the 5 relatives having 2 autoantibodies or more carried the DRB1*04-DQB1*0302 susceptible haplotype. In conclusion, this observational study confirms in a Tunisian population known epidemiological data and demonstrates the usefulness of follow-up to determine the predictive value of studied markers.