CD4 and type 2 diabetes mellitus: Due to the potential correlation of IL-15 levels and Tregs proportion in the CHB + T2DM group, CD4+CD25+CD127dim/− Tregs were stimulated with either 10 ng/mL or 100 ng/mL recombinant human IL-15 for 24 hours to analyze the response of IL-15 in different groups.