IL33 and rheumatoid arthritis: This inhibition translated to reduced secretion of CXCL8 and CCL2 by RA synovial fibroblasts stimulated with TNFα alone or the combination of TNFα, IL-1β and a TLR3 agonist.74,75 Thus, induction of intracellular IL-33 expression by IL-1 and TNFα may act as a negative feedback regulator of acute inflammatory responses by fibroblasts.