IL4 and periodontitis: IL-4 has been shown to inhibit the IL-1 induction of MMP-3 expression in human conjunctival fibroblasts [30], skin fibroblasts [31] and articular chondrocytes [32,33], as well as in synovial fibroblast cultures established from patients with osteoarthritis [34] and gingival fibroblast (HGF) cultures established from patients with periodontitis [35].