Interleukin 4

Interleukin 4 (IL-4) is a cytokine that induces differentiation of naive helper T cells (Th0 cells) to Th2 cells. Upon activation by IL-4, Th2 cells subsequently produce additional IL-4 in a positive feedback loop. The cell that initially produces IL-4, thus inducing Th0 differentiation, has not been definitively established. IL-4 has many biological roles, including the stimulation of activated B-cell and T-cell proliferation, and the differentiation of B cells into plasma cells. It is a key regulator in humoral and adaptive immunity.

Structure

IL-4 has a compact, globular fold (similar to other interleukins), stabilized by four disulfide bonds among its 129 amino acids. The structure of IL-4 is that of a single chain of four alpha helices, which are connected by loops.

Function

IL-4 induces B cells to switch to IgE production. It can also stimulate T cells, Mast cells, and macrophages to express Fc receptors and MHC class II proteins, which are involved in antigen presentation. IL-4 decreases the production of Th1 cells, macrophages, IFN-gamma, and IL-12 from macrophages and induces the expression of IL-1ra.

Clinical significance

IL-4 has been associated with several diseases, including asthma, rheumatoid arthritis, and cancer. In asthma, the IL-4 levels are elevated. In rheumatoid arthritis, IL-4 can suppress inflammation and tissue destruction. In cancer, IL-4 is thought to play a role in the growth and survival of certain types of cancer cells.

See also

• IL-13
• IL-2
• IL-10

References

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