STAT3 and systemic lupus erythematosus: IL-9 appears to promote B cell proliferation and immunoglobulin production, which could be blocked by inhibition of signal transducer and activator of transcription 3 (STAT3). In vivo treatment with neutralizing anti-IL-9 antibody decreased serum anti-dsDNA antibody titers and alleviated lupus nephritis in MRL/lpr mice, suggesting that IL-9 is a potential therapeutic target for SLE.