In vitro secretion of interleukin 2 and expression of IL-2 receptor in peripheral blood lymphocytes in high risk of insulin-dependent diabetes mellitus subjects.

Interleukin 2 (IL-2)--a Th1 lymphocyte-derived cytokine is at present considered to play an important role in the etiopathogenesis of insulin-dependent diabetes mellitus. In the previous studies increased, decreased and unchanged IL-2 levels in patients with recent onset of insulin-dependent diabetes mellitus (IDDM) were found. These differences could be a result of different metabolic status or/and a different stage of the autoimmune process. The aim of our study was to estimate in vitro secretion of IL-2 and CD25 antigen expression by the peripheral blood T lymphocytes in subjects at the preclinical stage of IDDM (prediabetes), but still without metabolic disturbances. In 27 first degree relatives of IDDM patients with antibodies against different pancreatic islet cell antigens (ICA, GADA, IAA, IA-2) CD25 antigen expression on peripheral blood lymphocytes T was measured by flow cytometry and IL-2 concentration in supernatants of 48 and 72 h cultures of peripheral whole blood with 10 microg/ml PHA was estimated by ELISA. The control group was comprised of 34 age and sex-matched healthy volunteers. In the studied high risk IDDM subjects the decreased CD25 expression in peripheral CD4+ lymphocytes T and a negative correlation between the percentage of CD25+ cells and islet cell antibodies (ICA) titres was observed. No differences in IL-2 levels in supernatants of 48 h and 72 h blood cultures was found in subjects with single antibody (ICA+) in comparison to healthy controls. A significant increase of IL-2 secretion at 72 h of PHA stimulation was shown in first degree relatives of IDDM patients with a combination of 3 or more antipancreatic-B cell antibodies. There were also a significant negative correlation between glutamic acid decarboxylase antibodies (GADA) titres and IL-2 levels in 72 h of culture. The present study suggests the involvement of IL-2 in the pathogenesis of IDDM. The estimation of CD25 antigen expression in the peripheral blood lymphocytes could be an additional immunological marker of identification of subjects in prediabetes.