We have begun to genetically map the high IFN-α trait in SLE, and found that a number of genetic variants which are associated with susceptibility to SLE are also associated with increased serum IFN-α, including variants of interferon regulatory factor 5 (IRF5) [15], interferon regulatory factor 7 (IRF7) [16], protein tyrosine phosphatase non receptor type 22 (PTPN22) [17], and osteopontin (SPP1) [18]. This evidence concerns the gene PTPN22 and systemic lupus erythematosus.