Circulating class II transplantation antigen-expressing T lymphocytes in children with insulin-dependent diabetes mellitus at diagnosis.

The occurrence of circulating class II antigen-expressing T lymphocytes was examined in 25 children with insulin-dependent diabetes mellitus using an indirect double immunofluorescence assay on prefixed cell samples. In order to exclude sensitization to heterologous insulin as a possible factor affecting the results, the patients were investigated at the day of clinical onset, before receiving insulin. An increased percentage of T cells (CD3+ cells) expressing class II antigens was seen in 19 out of 25 patients and class II expression was observed on cells within both the CD4+ and CD8+ T cell subsets. No correlation was found between the levels of class II expressing T cells and the individual degree of metabolic derangement or indicators of recent infection. Re-testing of 16 patients after one year on insulin treatment revealed a significant decrease of class II expressing T cell levels. Our data suggest that the increased levels of class II expressing T cells seen in IDDM of recent onset directly reflects immune reactions that are related to the disease process.