HLA type and the genetic risk for type 1 diabetes mellitus.

One hundred twenty-nine type 1 diabetic children and 176 non-diabetic siblings from the Louisville referral area were HLA typed by microlymphocytotoxicity technique. DR antigen frequencies were compared to frequencies for the Southeast USA population. Frequencies of DR3 and DR4 were significantly increased in both the diabetics and their unaffected siblings relative to the general population and DR2 was decreased. Forty-six percent of diabetic children possessed both DR3 and DR4 antigens while only 7% had neither. The findings are consistent with those in other geographical areas and give strong support to the role of DR3 and DR4 antigens as markers for diabetes susceptibility genes.