TNF and rheumatoid arthritis: These cells are highly activated and are one of the main producers of interleukin (IL)-1β and tumor necrosis factor-alpha (TNF-α), two essential proinflammatory cytokines required for the progression of RA because they are capable of inducing other proinflammatory cytokines and activating matrix metalloproteinases in autocrine and paracrine fashions [2].