Th2 dominance of T helper cell response to preproinsulin in individuals with preclinical type 1 diabetes.

In human type 1 diabetes (T1D) autoantibodies to insulin precede clinical disease, while little is known about the contribution of insulin-specific T lymphocytes-in particular, T helper (Th) subsets. Here we have studied the in vivo primed cytokine response to preproinsulin in peripheral blood mononuclear cells (PBMCs) and two major Th cell subsets-CD45RO+ memory cells and CD45RA+ naive/resting cells-in 35 individuals with HLA-DRB1*04, DQB1*0302 diabetes risk marker: 12 patients with T1D, 12 autoantibody-positive (Ab+) individuals, and 11 healthy controls. Cytokine secretion (TNF-alpha, IFN-gamma, IL-2, IL-4, IL-5, and IL-10) was measured in the supernatants of the cultures stimulated with 21 overlapping preproinsulin peptides as well as proinsulin and insulin. In Ab+ individuals our results reveal higher IL-4 levels in CD45RO+ memory cells and higher IL-5 levels in CD45RA+ naive/resting cells, while higher IL-2 production was found in PBMCs. In contrast, in PBMCs of T1D patients higher IFN-gamma and IL-10 secretion was found. Our data delineate characteristic cytokine patterns in peripheral T lymphocytes from patients at different stages of the T1D development.

Relationship between T and B cell responses to proinsulin in human type 1 diabetes.

In type 1 diabetes, humoral and cell-mediated responses to insulin and proinsulin are detectable. Autoantibodies to insulin are associated with impending disease in young individuals and are used as predictive markers to determine disease risk. The aim of this study was to investigate whether different cytokine patterns of cellular reactivity to insulin might serve as additional specific markers of disease maturation and might improve disease prediction in individuals at risk. We correlated T and B cell responses to insulin in subjects with increased genetic risk (HLA-DRB1*04, DQB1*0302) for diabetes with or without islet autoantibodies (Ab+ subjects and controls, respectively) and HLA-matched patients. Peripheral blood mononuclear cells were stimulated with 15 overlapping proinsulin peptides (16-mer), and proinflammatory Th1 (IFNgamma) and anti-inflammatory Th2 (IL-4) cytokines were analyzed. We observed a simultaneous increase in IL-4 and IFNgamma secretion in early islet autoimmunity of Ab+ subjects, but not in insulin-treated T1D patients. Furthermore, the increase in IL-4 secretion in Ab+ subjects was associated with insulin autoantibody responses. There was no correlation of either IFNgamma or IL-4 secretion with insulin antibody responses in patients already treated with exogenous insulin. In conclusion, our findings reveal that quantification of cytokine responses to proinsulin in peripheral blood may prove to be a promising specific marker of diabetes progression and could, in addition to insulin autoantibodies, be used in the prediction of type 1 diabetes.