Reduction of tumor necrosis factor α and interleukin-1β levels in human synovial tissue by interleukin-4 and glucocorticoid

The effects of recombinant human interleukin-4 (IL-4) and the glucocorticoid, dexamethasone, on tumor necrosis factor α (TNFα) and interleukin-1β (IL-1β) levels in cultures of rheumatoid and osteoarthritic synovial tissue were studied. Low concentrations of IL-4 and dexamethasone suppressed the levels of both cytokines in the supernatants of both types of tissue after stimulation with lipopolysaccharide (LPS); the IL-1β and TNFα levels were measured by ELISA. It is suggested that it is the monocyte/macrophage in the synovial tissues that is responsive to the inhibitors. It is proposed that glucocorticoids may act on synovial tissue in this manner in vivo and IL-4 may do so if administered intraarticularly.