A minor subset of HLA-DR3 haplotypes is preferentially increased in type 1 (insulin-dependent) diabetes.

We have been using human T-lymphocyte clones specifically sensitized to detect leucocyte antigens of Type 1 (insulin-dependent) diabetic patients in the hope of detecting novel HLA antigens associated with Type 1 diabetes. We previously described two such clones which define a new class II HLA antigen, Boston-1 (BO1). BO1 is found mainly on cells of persons with particular HLA-DR antigens and, of potential significance for diabetes, BO1 identifies a distinctive subset of DR3 haplotypes. We report here that BO1+ DR3 haplotypes are overrepresented in Type 1 diabetes. That is, significantly more of the DR3-positive subjects are BO1-positive in the patient group (31%) than in the control group (8%), suggesting that a diabetes-susceptibility gene may be more common on the BO1+ than on the BO1- DR3 haplotypes. Alternative interpretations are also discussed.