Interleukins

Interleukins

PKGhatak,MD

Interleukins:

In 1979, an international committee coined the term Interleukin (IL) to identify chemicals secreted by Immunocytes. Interleukins are a part of Cytokines. Cytokines are proteins, that act as chemical messengers of the immune system and are secreted by both immunocytes and non-immunocytes. Cytokines include Chemokines, Lymphokines, Interferons, Tissue Necrosis Factor (TNF), Colony Stimulating Factors(CGF) and ILs.

Interleukins are also secreted by Endothelial cells, Enterocytes of the intestine, and certain Connective tissues. Interleukins initiate the activation and differentiation of immunocytes and also various other aspects of immune cell functions. ILs can act both as stimulators and inhibitors of inflammation.

In humans so far, 17 ILs are known and 50 genes are identified controlling ILs. Some genes control more than one IL. IL-2 and IL-6 are often mentioned in the discussion of the pathophysiology of illnesses.

ILs are stimulators of inflammation.

These ILs are IL-1, IL-6, IL-12, IL-18 and IL-23

The most pro-inflammatory Cytokines are IL-1 beta and TNF alpha.

Pro-inflammatory ILs activate CD2, CD4, CD8, CD27, CD134 and CD137.

Inhibitors of inflammation ILs are-

IL-10, IL-6, IL-1 beta. They activate CD80, CD152, CD160, and CD223.

A synopsis of the origin and actions of Interleukins:

IL -1. IL-1 is active in the human Hippocampus and is involved in memory formation.

IL 2. IL -2 was previously called Lectin. It is produced by CD12, CD122 and CD132. IL-2 stimulates the growth and differentiation of T-cells, it also stimulates immunoglobulin production by B cells.

IL-3. IL-3 is secreted by and CD123 and CD 131. It stimulates the differentiation and growth of granulocytes of the blood and tissue macrophages.

IL-4. IL-4 is produced by CD124 and CD132 cells. It stimulates B cell proliferation and mutation. It also stimulates B-cells to produce immunoglobulins.

IL-5. IL-5 is secreted by CD 125 and CD 131. IL-5 initiates the differentiation of eosinophils from the hemopoietic stem cells.

IL-6. IL-6 is a major IL in humans. CD126 T and CD130 T cells produce IL-6. IL-6 accelerates the production of Interferon beta2 by the B-cells. In the liver, IL-6 stimulates the production of acute phase reactants and GCSF.(granulocyte colony-stimulating factor).

IL-10. IL-10 is the major inhibitory Interleukin in humans. It is produced by CD210 cells. IL-10 counteracts the actions of Interferon gamma and IL-2, IL-3. TNF and GCSF.

IL-12. IL-12 increases the cytotoxic function of Natural Killer (NK) cells. In parasitic infestation, like Leishmaniasis and toxoplasma and measles infection, IL-12 mounts a cellular response. IL-12 plays an important immunological function in HIV infection, Multiple Scerosis and Chron's disease.

IL-17. IL-17 is produced by CWD 217 cells. IL-17 stimulates osteoclastogenesis and angiogenesis.

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