IFN-ζ

Interferon-zeta (IFN-ζ), better known as limitin, is a murine type I interferon that structurally and functionally sits closest to the IFN-α family yet is encoded by a separate gene, Ifnz, located outside the murine interferon cluster on chromosome 4. Identified in 2000 from a mouse bone marrow stromal cell line, limitin is a 182-amino-acid secreted protein sharing about 50% homology with murine IFN-α. It binds the common IFNAR1/IFNAR2 receptor but triggers characteristically weak activation of ISGF3 compared with IFN-α and IFN-β, resulting in strong inhibition of B-cell lymphopoiesis and dendritic cell development with minimal antiviral and cytostatic effects, a profile exploited experimentally to dissect receptor-ligand determinants of interferon pleiotropy. Limitin expression is induced in lymphoid tissues by viral mimetics, and its immunosuppressive bias-sparing T cells while suppressing antibody production-suggests a role in regulating humoral immunity; no direct human orthologue has been confirmed, although related sequences exist in primate genomes.