DEFECTIVE HLA CLASS-II EXPRESSION IN MONOCYTES OF TYPE-1 DIABETIC-PATIENTS

Activation of T-helper cells is modulated by the intensity of HLA clas s II expression on antigen-presenting cells. We evaluated whether any abnormalities could be found in the expression of HLA-DR and -DQ molec ules on monocytes in type 1 diabetic subjects. DR and DQ molecules wer e induced by human recombinant interferon-gamma on cultured peripheral blood monocytes obtained from children with type 1 diabetes (N = 28), their siblings (N = 18) and unrelated healthy controls (N = 21). The response in DQ induction varied considerably between different individ uals, but the average responsiveness was significantly lower in patien ts compared to siblings and unrelated controls. In addition to the dia betic subjects deficient DQ induction was also observed in three sibli ngs. One of them had high levels of islet cell antibodies and presente d with diabetes 6 months later, and another had active rheumatoid arth ritis. The response in DR induction was also slightly lower in patient s than in siblings, but did not differ from that in unrelated controls . The results suggest abnormalities in the regulation of HLA class II expression in type 1 diabetic subjects possibly reflecting the ongoing autoimmune process.