MAJOR HISTOCOMPATIBILITY CLASS-II GENES POLYMORPHISM IN INSULIN-DEPENDENT DIABETES-MELLITUS WITH OR WITHOUT ASSOCIATED THYROID AUTOIMMUNITY

Insulin dependent diabetes mellitus (IDDM) is sometimes associated wit h extrapancreatic organ-specific autoimmune diseases, but whether this phenotype results from a peculiar genetic profile is still unclear. T he allelic distribution of the major histocompatibility complex (MHC) class II genes (HLA-DRB1, DQA1, DQB1 and TAP) was analysed in 143 pati ents with IDDM alone by comparison with 52 IDDM patients with autoimmu ne thyroid disease (IDDM/AITD). The frequency of the DQB10301 IDDM-pr otective phenotype seemed to be lower in IDDM than in IDDM/AITD patien ts (16.8% vs 30.5% respectively, p = 0.02). By contrast, the frequency of the DRB104-DQB1*0302 IDDM-predisposing phenotype was higher in ID DM than in IDDM/AITD patients (91.3% vs 76.1% of DR4-positive patients respectively, p = 0.007), but these differences were not significant after correcting the p values, except in the case of the DRB 0405-DQB 10302 combination (21.3% vs 2.4% of DR4-positive patients, Pc = 0.05) . Furthermore, all differences disappeared when patients were marched for age at IDDM-onset. Our data do not long give support for a particu lar role of MI-IC class II genes in favouring the occurence of thyroid autoimmunity in IDDM patients, but rather suggest that some class II alleles or residues might determine the rapidity of progression to IDD M in genetically susceptible individuals. The involvement of non-MHC g enes and/or environmental factors remains to be determined. (C) Americ an Society for Histocompatibility and Immunogenetics, 1998. Published by Elsevier Science Inc.