Preferential transmission of diabetic alleles within the HLA gene complex.

Several studies suggest a higher incidence of insulin-dependent diabetes mellitus (IDDM) among the offspring of men with the disease than among those of female diabetics. Differential transmission by the father of genes that predispose to diabetes may explain this phenomenon. To test this hypothesis, we examined parent-to-offspring transmission of HLA haplotypes and DR (D-related) alleles in 107 nuclear families in which a child had IDDM. We observed that fathers with a DR4 allele were significantly more likely to transmit this allele to their diabetic or nondiabetic children than were mothers with a DR4 allele (72.1 vs. 55.6 percent, P less than 0.001). No differences between parents were observed for HLA-DR3; however, DR3 was transmitted significantly more than 50 percent of the time from either parent (P less than 0.001). These data suggest that differential parental transmission of the HLA-DR4-linked diabetes-predisposing allele may explain the higher risk of diabetes among children of diabetic fathers than among those of diabetic mothers. In addition, the excess transmission of diabetogenic HLA alleles from parent to offspring may explain how these deleterious genes continue to recur at such high frequencies in the general population.