Interleukin-25

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 the induction, progression and control of T-cell-mediated cytotoxic immune reactions and B-cell activation (antibody production). They are mainly produced and secreted by stimulated leukocytes, monocytes and macrophages. To date, around 38 different interleukins have been clearly identified. Each cytokine of the interleukin group is assigned a nomenclatural 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 are involved in the fine regulation of immune reactions, for example by regulating the synthesis of related interleukins. Interleukin-25 is a pro-inflammatory cytokine that belongs to the interleukin-17 family together with the interleukins IL-17, IL-21 and IL-22. Interleukin-25 binds to its receptor IL-25R.

Interleukin-25 belongs to the interleukin-17 family. It is homologous to IL-17E and influences immunological processes of Th2 immunity (see interleukin-17 below). Both cytokines are ligands for the cytokine receptor IL17RB. IL-25 induces the expression of other cytokines, such as IL4, IL5, IL8 and IL13.

The cytokine is produced and secreted by type 2 helper T cells, mast cells and eosinophil granulocytes. Its expression can be induced by allergens, including helminthic parasites.

Together with its receptor, IL-25 plays an important role in modulating the type 2 immune response, especially the pro-inflammatory functions of eosinophil granulocytes in allergic bronchial asthma and other allergic diseases such as chronic rhinosinusitis with nasal polyps (CRSwNP). Plasma levels of IL25 and IL25R (IL17RA/IL17RB/IL17RA/RB) are elevated in patients with allergic bronchial asthma.

Although IL25 and IL17 are members of the same cytokine family, both cytokines appear to play opposing roles in the pathogenesis of autoimmune diseases. IL25 is involved in the pathogenesis of allergic processes. In a second function (note: demonstrable dualism of many cytokines) IL25 controls and reduces Th1/Th17-triggered immunological processes.

IL25 is a cytokine that controls intestinal immunity. It is involved in the chronic inflammatory processes of the intestine. Furthermore, the cytokine has an antitumor effect, which has been shown in a number of malignancies, including carcinomas of the pancreas, colon, lung and breast.

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