CD4 and type 1 diabetes mellitus: Despite a significantly increased frequency of PD-1+ cells in naive CD4+, naive CD8+, and CD8+ Temra subgroups in T1D participants, PD-1 expression intensity (MFI) was reduced in T1D participants in most subgroups analyzed: CD4+ Tem, CD4+ Temra, CD4+ Tcm and CD8+ Tcm.