Expansion of FasL-Expressing CD5(+) B Cells in Type 1 Diabetes Patients

Fas ligand drives insulitis in the non-obese diabetic mouse model of type 1 diabetes (T1D) and negatively regulates IL-10-producing (IL-10(pos)) CD5(+) B cells in pancreata. Relevance of these phenomena to the human disease is poorly understood. Here, using splenocytes from T1D, autoantibody (Ab(+)), and non-diabetic (ND) human subjects, we show that a subpopulation of CD5(+) B cells that is characterized by expression of FasL (FasL(hi)CD5(+)) was significantly elevated in T1D subjects, many of whom had significantly reduced frequency of IL-10(pos)CD5(+) B cells compared to Ab(+) subjects. The majority of FasL(hi)CD5(+) B cells did not produce cytokines and were more highly resistant to activation-induced cell death than their IL-10(pos)CD5(+) counterparts. These results associate expansion of FasL-expressing CD5(+) B cells with T1D and lay the groundwork for future mechanistic studies to understand specific role in disease pathogenesis.