JAK2 and systemic lupus erythematosus: To clarify the gene expression in the IFN receptor signaling pathway, we performed qPCR analyses of JAK1 and JAK2, TYK2, STAT1 and STAT2, and IRF1. Compared with that of HCs, the mRNA level of JAK2 was decreased in AIBD patients (HC vs. AIBD, P < 0.0001), and the levels of JAK1 and JAK2 were also decreased in SLE patients (JAK1, HC vs. SLE, P < 0.0001; JAK2, HC vs. SLE, P < 0.05).