Associations of MHC class II alleles with insulin-dependent diabetes mellitus (IDDM) in patients from North India.

Thirty-four insulin-dependent diabetes mellitus (IDDM) patients from North India were studied with respect to their HLA class II alleles including those of the DRB1, DQA1, DQB1 and DPB1 loci, using the polymerase chain reaction (PCR) and hybridization with sequence-specific oligonucleotide probes (SSOP). They were compared with the class II alleles of 94 normal adult controls from the same ethnic background. The results show a statistically significant increase of DRB103011 (p < 0.00001), DQB10201 (p < 0.007), DQA10501 (0.0027) and DPB12601 (p < 0.0042) in patients compared to controls. DR04 was not significantly increased. However, homozygosity for DRB103011 was increased more than expected. DRB11501 and 1502 did not show a significant decrease in the patients. However, DRB10701 was decreased significantly, but this difference did not remain significant when the p value was corrected for the number of alleles tested. Similarly, DPB12601 was increased significantly in the patients but did not remain significant after p was corrected for the number of alleles tested. However, DPB12601 was increased, and remained significant after correction, in patients not having HLA-DR3. We also studied the possible role of aspartic acid at codon 57 of the DQ beta chain in protection against development of diabetes, and arginine at codon 52 of the DQ alpha chain in susceptibility. We observed an increase in non-Asp57 alleles in DQ beta and Arg52 in DQ alpha in the patients, however, this effect seems to be due to the fact that the most prevalent haplotype in diabetic patients: DRB103011-DQA10501-DQB10201, has DQB1 and DQA1 alleles which carry non-Asp57 and Arg52, respectively.