PTPRC and type 1 diabetes mellitus: Over 25 years ago, T cells from T1D were shown to have an activation defect related to the CD45 protein and its splice variants, CD45RA and CD45RO.20, 24, 25 Here we show in T1D a similar activation defect specifically in Tregs, as manifest by a lifelong overabundance of rTregs and an under abundance of aTregs.