Interleukin-18

Interleukin-18 (IL-18) is a protein that in humans is encoded by the IL18 gene. It is a pro-inflammatory cytokine that belongs to the interleukin family of cytokines, which are small cell-signaling protein molecules that are secreted by numerous cells and are involved in a variety of cellular activities such as cell proliferation, differentiation, and apoptosis.

Structure and Function

IL-18 is an 18 kDa protein that is synthesized as a precursor 24 kDa molecule. The precursor is cleaved into an active cytokine by caspase 1 (CASP1) and is secreted from the cell. IL-18, along with interleukin 12, induces cell-mediated immunity following infection with microbial products like lipopolysaccharide (LPS). The combination of this cytokine and IL12 has been found to inhibit IL4 dependent IgG1 and IgE production and enhance IgG2a production in B cells. IL-18 binds to the interleukin-18 receptor, and the complex formed is recognized by the interleukin 18 binding protein (IL18BP), which inhibits the activity of IL-18.

Clinical Significance

IL-18 has been associated with several immune responses and inflammatory disorders. It is known to play a crucial role in the production of interferon-gamma (IFN-γ) from T cells and natural killer cells, and is thought to influence Th1/T helper cell responses. Elevated levels of IL-18 have been linked to diseases such as rheumatoid arthritis, inflammatory bowel disease, and autoimmune diseases.

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Structure of Interleukin-18

Research and Therapeutics

Research is ongoing to develop therapeutic agents that can modulate the activity of IL-18. Several IL-18 binding proteins and IL-18 inhibitors are currently under investigation for their potential in treating various inflammatory and autoimmune diseases.

See Also

• Interleukin
• Cytokine
• Inflammation
• Autoimmune disease