TNFSF13B and rheumatoid arthritis: HIF-1α accumulates even under normoxic conditions in an inflammatory condition.11 The high expression level of HIF-1α detected in synoviocytes may have a role in the pathogenesis of RA.8, 9 Therefore, TNF-α-induced BAFF expression could be regulated by the association between HIF-1α and the BAFF promoter.