To examine the effect of this combination we stimulated RA FLS with 10 ng/ml of the Th1 cytokines TNFα and IL-1β or the Th2 cytokines IL-4 and IL-13 in 21% or 1% oxygen for 24 hours and investigated changes in gene induction by quantitative PCR, Western blotting and using a HIF DNA binding assay. The gene discussed is IL4; the disease is rheumatoid arthritis.