The immunological ménage à trois promotes inflammation in Type 2 diabetes. (54.14)

Type 2 diabetes (T2D) is an inflammatory disease promoted by changes in immune cell function. Monocytes and T cells play roles in T2D inflammation as evidenced, in part, by our demonstration of pro-inflammatory T cell subset skewing in T2D patients. However, the role of cross-talk amongst immune system cells in T2D is poorly unstudied. PBMC depletion studies showed that T2D patient T cells, unlike non-diabetic (ND) donor cells, required monocytes to maintain IL-17 hyper-secretion. In contrast, B cell depletion did not affect T2D Th17 function, but surprisingly, B cell depletion from non-diabetic (ND) mixed cell cultures significantly elevated Th17 function. Based on the role B cell IL-10 plays in inflammation resolution, we tested the hypothesis that IL-10 regulates immune cell cross-talk to block Th17 function. IL-10 addition to B cell-depleted PBMCs decreased IL-17 to “healthy” levels in both ND and T2D samples, indicating that both cell types are physiologically capable of interpreting the anti-inflammatory signals from B cells despite the presence of pro-inflammatory monocytes in T2D samples. Critically, unlike ND B cells, T2D B cells fail to secrete IL-10, thus lack of B cell IL-10 in T2D samples compounds elevated pro-Th17 cytokine production by monocytes. We conclude that IL-10 can block monocyte-mediated increases in Th17 function, and that lack of B cell IL-10 in T2D associates with IL-17-induced inflammation thus metabolic imbalance.