In T1D, the frequency of CD19+CD10+CD27−CD24hiCD38hi cells has been reported to be increased in T1D patients, as well as in non-diabetic carriers of the PTPN22 Trp620 (rs2476601; Arg620Trp) non-synonymous risk allele 24. Here, PTPN22 is linked to type 1 diabetes mellitus.