What Are Cytokines?

Question: What Are Cytokines?

Cytokines serve as molecular messengers between cells. With regard to arthritis, cytokines regulate various inflammatory responses. Cytokines are often discussed in arthritis research but are not well understood by most patients. What exactly are cytokines? Are there different kinds of cytokines?

Answer:

Cytokines are proteins that are produced by cells. Cytokines interact with cells of the immune system in order to regulate the body's response to disease and infection. Cytokines also 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 that works by inhibiting IL-1 binding 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), and Humira (adalimumab) are TNF blockers. Other anti-cytokine therapies are in development.

_Sources:

Cytokines in the pathogenesis of rheumatoid arthritis. I. McInnes and G. Schett. Nature Immunology. June 2007
http://www.nature.com/nri/journal/v7/n6/abs/nri2094.html

Cytokines. BioBasics. 4/24/2006.
http://biobasics.gc.ca/english/View.asp?x=778

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