CD4 and diabetes mellitus: There is increasing evidence that strategies to induce Foxp3+CD25+CD4+ Treg cells may efficiently control T1D.21, 46, 47, 48 Ppins-specific DNA vaccines (e.g., encoding the ppinsΔA12-21) elicited a systemic Foxp3+CD25+CD4+ Treg cell immunity in PD-L1−/− or PD-1−/− mice that selectively suppressed CD8+ T cell-mediated (and Kb/A12-21-specific) diabetes induction.18