Interleukin-24

Interleukins (from Latin/Greek inter = between; leukos = white; kinein = to move) are a group of endogenous, short-chain regulatory proteins (cytokines) of the immune system (IL1-IL38). Interleukins are mediators for induction, course and control of T-cell-mediated cytotoxic immune reactions as well as B-cell activation (antibody production). They are mainly formed and secreted by stimulated leukocytes, monocytes and macrophages. So far, about 38 different interleukins have been clearly identified. Each cytokine of the interleukin group is nomenclatically assigned a number for its classification (IL-1 to IL-38).

Some structurally related substances have been grouped into families. Their members often have a similar function or participate in the fine regulation of immune reactions, for example by regulating the synthesis of related interleukins.

IL-24 belongs to the interleukin-10 family, with the following related interleukins: Interleukin-10, homologous to interleukins-19, -20, and interleukins -22, -26, whose signals are converted by two heterodimeric receptors: IL-20R1/IL-20R2 and IL-22R1/IL-20R2. Interleukin-24 was also known as "melanoma differentiation-associated 7" (also called mda-7) after its function as a tumor suppressor protein was discovered. Interleukin 24 (IL-24) is encoded in humans by the IL24 gene, which is located on chromosome 1.

Interleukin-24 is produced by activated monocytes, macrophages and T helper cells and acts on non-hematopoietic tissues such as skin, lungs and reproductive tissues.

As a so-called "tumour suppressor cytokine", IL-24 exerts a control on the growth and survival of cells. The cytokine exerts a tumour-selective proapoptotic suppressor function on a number of tumours, including breast carcinoma, melanoma and B-cell lymphomas. It also inhibits tumour-induced angiogenesis. Overexpression of interleukin-24 in melanoma cell cultures leads to activation of the phosphorylation of mitogen-activated protein kinase 14 - MAPK7/P38-, and of heat shock protein 1, and ultimately to apoptosis of melanoma cells.

Furthermore, the cytokine plays an important pathogenetic role in wound healing, arthritis and psoriasis. An antiviral effect on various influenza A virus subtypes has been experimentally proven. The antiviral effect correlates with caspase-3 activity.

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