Meteorin-like/Meteorin-β Is a Novel Immunoregulatory Cytokine Associated with Inflammation.

We have described a novel cytokine encoded by a gene called Meteorin-like (). Metrnl is a small (∼28 kDa) secreted protein expressed by activated macrophages and barrier tissues (mucosa and skin). Metrnl production by bone marrow macrophages is induced by several cytokines including TNF-α, IL-17α, IL-12, and IL-4 and inhibited by IFN-γ and TGF-β.

Identification of IL-40, a Novel B Cell-Associated Cytokine.

We describe a novel B cell-associated cytokine, encoded by an uncharacterized gene (; chromosome 17 open reading frame 99), that is expressed in bone marrow and fetal liver and whose expression is also induced in peripheral B cells upon activation. is only present in mammalian genomes, and it encodes a small (∼27-kDa) secreted protein unrelated to other cytokine families, suggesting a function in mammalian immune responses. Accordingly, expression is induced in the mammary gland upon the onset of lactation, and a mouse exhibits reduced levels of IgA in the serum, gut, feces, and lactating mammary gland.