Interleukin-29

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 in the interleukin group is nomenclaturally assigned a number for its classification (IL-1 to IL-38, as of 2017).

Interleukin-29 (IL-29), also known as IFN lambda, is a 179 amino acid, non-glycosylated, 19.9 kDa protein.IL-29 is encoded in humans by the IFNL1 gene on chromosome 19, in mice it is a pseudogene, i.e. the IL-29 protein is not formed in them.

Like the homologous interleukin-28, with which interleukin-29 has a high amino acid sequence similarity, IL-29 is a member of the interleukin-10 family. It is a type III interferon (hence the designation IFNgamma1).

IL-29 is expressed by virally infected cells, including Th1-7 cells. IL-29 therefore plays an important role in the defence against microbial and viral infections. Furthermore, the cytokine can be detected in lesional synovial macrophages and fibroblasts in patients with rheumatoid arthritis. Interleukin-29 has been shown to be expressed in psoriatic skin, but not in the skin of the neurodermatitis patient.

In rheumatoid arthritis (RA) elevated interleukin-29 levels are measured, which may show a positive correlation with rheumatoid factor, anti-CCP antibody and clinical activity.

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