The role of cytokines
Cytokines are natural mediators of cell function.1 They transmit information between cells, mediate inflammatory reactions, and regulate cell growth and differentiation.1,2 Cytokines work either in synergy with other cytokines, promoting and supplementing their effects, or in opposition to them.1 Their targets may be the cells that produced them or adjacent cells.1 Some cytokines are capable of inducing production of other cytokines by binding to specific receptors on target cells. Once activated, these cells release more cytokines, setting up a cytokine cascade in the synovium.3
The cytokine network is largely self-regulating, with a balance of pro- and anti-inflammatory cytokines.4 As shown here, proinflammatory cytokines such as TNF induce inflammation by binding to appropriate cell-surface receptors. Serving as a counterbalance are anti-inflammatory cytokines such as soluble TNF-receptors, which intercept and neutralize TNF.5
References: 1. Arend WP, Dayer J. Cytokines and growth factors. In: Kelley WN, ed. Textbook of Rheumatology. Vol 1. 4th ed. Philadelphia, Pa: W.B. Saunders Company; 1993;227-247. 2. Carpenter AB. Immunology and inflammation. In: Wegener ST, ed. Clinical Care in the Rheumatic Diseases. Atlanta, Ga: American College of Rheumatology; 1996:9-14. 3. Baumgartner SW. Tumor necrosis factor inactivation in the management of rheumatoid arthritis. South Med J. 2000;93:753-759. 4. Arend WP. Mediators of inflammation, tissue destruction, and repair: growth factors and cytokines. In: Klippel JH, ed. Primer on the Rheumatic Diseases. 11th ed. Atlanta, Ga: Arthritis Foundation; 1997:39-64. 5. Moreland LW. Inhibitors of tumor necrosis factor: new treatment options for rheumatoid arthritis. Cleve Clin J Med. 1999;66:367-374.
