PTPN22 and autoimmune disease: PTPN22 has four proline-rich motifs (P1-P4) at the C-terminus, and the P1 motif interacts with the SH3 domain of CSK [29,33]; rs2476601 (GRCh38 NC_000001.10:g.114377568A>G) is located in the P1 motif of PTPN22; rs2476601 is associated with more than ten autoimmune diseases, including T1D [26,27,28].