High-resolution DNA typing in immunoglobulin A deficiency confirms a positive association with DRB1*0301, DQB1*02 haplotypes.

Selective immunoglobulin A (IgA) deficiency, the most common form of primary immunodeficiency, is related to the HLA genes. Previous studies demonstrated associations with particular HLA-DR-DQ haplotypes and a neutral amino acid at position 57 of the DQbeta chain was implicated in the susceptibility to selective IgA deficiency. In this study we reanalyzed the reported findings by high-resolution DNA typing of the loci DRB1, DQB1 and DQA1. We compared the typing results of 74 IgA-deficient individuals, detected by screening of blood donors, with those taken from 111 healthy controls. Results confirmed a strong positive association with DRB1*0301, DQB1*02 and a negative association with DRB1*1501, DQB1*0602. Considering the molecular interactions between HLA class II alleles and the peptides bound we conclude that the amino acid at position 57 of the DQbeta chain may contribute to the susceptibility to selective IgA deficiency, but not determine it. An extended statistical analysis strengthened the hypothesis that selective IgA deficiency might be communicated by the distinct haplotype DRB1*0301, DQB1*02.