What Are Cytokines?

Cytokines Are Molecular Messengers

Cytokines in an immune reaction.
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Cytokines serve as molecular messengers between cells. Cytokines are proteins that are produced by cells. With regard to arthritis, cytokines regulate various inflammatory responses. Cytokines interact with cells of the immune system in order to regulate the body's response to disease and infection, as well as mediate normal cellular processes in the body.

Types of Cytokines

Cytokines are diverse, meaning, they are not all alike.

The body produces different types of cytokines:

  • colony stimulating factors (stimulate production of blood cells)
  • growth and differentiation factors (function primarily in development)
  • immunoregulatory and proinflammatory cytokines (interferon, interleukins, and TNF-alpha that function in the immune system)

How Cytokines Work

The immune system is complex -- different types of immune cells and proteins do different jobs. Cytokines are among those proteins. Explaining how cytokines work is difficult. It's a lesson in cell physiology. But to understand inflammation, you must understand the role that cytokines play.

Cytokines are released by cells into the circulation or directly into tissue. The cytokines locate target immune cells and interact with receptors on the target immune cells by binding to them. The interaction triggers or stimulates specific responses by the target cells.

Overproduction of Cytokines

Overproduction or inappropriate production of certain cytokines by the body can result in disease.

For example, it has been found that interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNF-alpha) are produced in excess in rheumatoid arthritis where they are involved in inflammation and tissue destruction.

Biologic Drugs Are Cytokine Inhibitors

Biologic drugs have been developed to inhibit IL-1 or TNF-alpha.

Kineret (anakinra) was developed as a treatment for rheumatoid arthritis and works by inhibiting the binding of IL-1 to its receptor. TNF-alpha inhibitors (also called TNF blockers) bind TNF and prevent TNF from attaching to cell surface receptors. Enbrel (etanercept), Remicade (infliximab), Humira (adalimumab), Simponi (golimumab), and Cimzia (certolizumab pegol) are TNF blockers. Actemra (tocilizumab) binds IL-6.

More biologic drugs are in development. At the 2015 Annual Meeting of the American College of Rheumatology, results were presented from a pivotal Phase 3 study (named SARIL-RA-TARGET) of sarilumab, an investigational, human antibody against the IL-6 receptor. Sarilumab binds with high affinity to the IL-6 receptor, blocking the binding of IL-6 and disrupting the cytokine-mediated inflammatory signaling. The study met both its primary endpoints of improvement in signs and symptoms of rheumatoid arthritis and improvements in physical function.


Growth Factors and Cytokines. Primer on the Rheumatic Diseases. Edition 12. Published by the Arthritis Foundation.

Regeneron and Sanofi Present Results from Pivotal Phase 3 Study of Sarilumab at American College of Rheumatology Annual Meeting. Regeneron. November 8, 2015.

Cytokines in the pathogenesis of rheumatoid arthritis. I. McInnes and G. Schett. Nature Immunology. June 2007

Cytokines. BioBasics. 4/24/2006.

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