In agreement with this notion, several genes with a role in IFN signaling, such as IRF5, IRAK1, STAT4, SPP1, TNFAIP3, and PTPN22, also have SLE-predisposing variants, which are associated with high levels of type I IFNs and increased expression of IFN-inducible genes [17,18,19,20,21]. Here, PTPN22 is linked to systemic lupus erythematosus.