TNF and rheumatoid arthritis: IL-17A induces the release of chemokines and cytokines (IL-1β, IL-6, IL-8, RANKL, TNF), matrix metalloproteinases, nitric oxide and prostaglandin E2 from fibroblasts, osteoblasts, chondrocytes and macrophages, all cells involved in RA pathogenesis9, 11–14.