ANALYSIS OF ANTIBODY MARKERS, DRB1, DRB5, DQA1 AND DQB1 GENES AND MODELING OF DR2 MOLECULES IN DR2-POSITIVE PATIENTS WITH INSULIN-DEPENDENTDIABETES-MELLITUS

HLA-DR2 is negatively associated with insulin-dependent diabetes melli tus (IDDM). The aim of the present study was to analyze DR2-positive p atients among 425 consecutively diagnosed unrelated Swedish children w ith IDDM and in 367 matched controls. HLA-DRB, -DQA and -DQB were dete rmined by Tag I restriction fragment length polymorphism analysis. Amp lification by polymerase chain reaction (PCR) and hybridization with s equence-specific oligonucleotide probes was done for DQA1, DQB1 and DR B1 and DRB5. DR2 was positive in 11/425 patients (3%) and 101/367 (28% ) controls (OR 0.07, p<0.0001). Of the 11 DR2-positive patients, PCR w as done in 10, of whom 8 were positive for DRB1()1601-DRB5(*)0201 com pared to 4/96 (4%) controls (OR 92.0; p<0.001) while the remaining 2 w ere positive for DRB1()1501-DRB5(*)0101 compared to 92/96 (96%, OR 0. 01; p<0.001). In 2 patients, a recombination between the haplotypes DQ B1()0502-DQA1(*)0102 (DQ5)-DRB1(*)1601-DRB5(*)0201 (DR16 Dw21) and DQ B1()0301-DQA1(*)0501 (DQ7)-DRB1(*)1602-DRB5(*)0202 (DR16 Dw22) was ob served resulting in the DQB1()0301-DQA1(*)0501 (DQ7) DRB1(*)1601-DRB5 ()0201 (DR16 Dw22) haplotypes. The second haplotype was DR3 DQ2 in 6/ 11 and DR4 DQ8 in 2/11 DR2-positive patients. In all 3 DQB1()0602-DQA 10102-DR15-positive patients the second haplotype was DR3-positive. I n order to test whether physicochemical properties of the DR2 molecule s were associated with IDDM, we constructed three-dimentional models o f the peptide binding and T-cell recognition sites (alpha 1 and beta 1 domains) of five subtypes of DR2-DRB1, based on the published DR1 cry stal structure. No correlations were observed for DR molecule physicoc hemical properties and diabetes susceptibility. Islet cell antibodies, insulin autoantibodies and GAD65 antibodies, were measured in DR2-pos itive patients (n = 11) and controls (n = 101). Despite the presence o f the DR2 haplotype the antibody markers were significantly elevated i n the patients compared to the controls (GAD65 3/10 patients and 2/101 controls; ICA 7/11 patients and 1/101 controls and IAA 3/11 patients and 0/101 controls). In conclusion, of the five subtypes of DR2, only one, the DRB1()1501, DRB5*0101, DQB1(*)0602-DQA1(*)0102 haplotype, wa s negatively associated with IDDM. DQ may therefore confer more protec tion from the disease than DR.