These SLE-associated variants encode proteins involved in cytokine signaling (e.g., signal transducer and activator of transcription 4 [STAT4]) and in the efficiency of signaling downstream of T- and B cell surface antigen receptors (e.g., protein tyrosine phosphatase non-receptor type 22 [PTPN22], tyrosine-protein kinase LYN, B cell scaffold protein with ankyrin repeats [BANK], B lymphocyte tyrosine kinase [BLK] and tumor necrosis factor-α-induced protein 3 [TNFAIP3]) [15,47]. Here, PTPN22 is linked to systemic lupus erythematosus.