Limitin: an interferon-like cytokine without myeloerythroid suppressive properties

Limitin is an interferon (IFN)-like cytokine that we recently identified an d cloned on the basis of its ability to arrest the growth or kill lympho-he matopoietic cells. This 182 amino acid protein has approximately 30% sequen ce identity with IFN-alpha, IFN-beta, and IFN-omega. Limitin binds to the I FN-alpha/beta receptors and induces IFN regulatory factor-1, thereby indica tings that limitin constitutes a new prototype of the type I IFN family. As with previously known IFNs, limitin inhibited B lymphopoiesis in vivo as w ell as in vitro. III addition, limitin not only modified the proliferation and function of peripheral T lymphocytes, natural killer cells, and bone ma rrow stromal cells but also had antiviral activity. Therefore, limitin is a multifunctional cytokine with several potential cellular targets. Because to date we have found no influence of limitin on normal myeloid and erythro id progenitors, limitin is unique among the IFNs, Type I IFN family contain s TFN-alpha, IFN-beta, IFN-omega, and IFN-tau, and IFN-alpha is composed of at least 14 subtypes. All IFNs have antiproliferative, immunomodulatory, a nd antiviral effects and influence to each other in the body. Limitin shoul d play a role in the complex IFN network, and its human homologue would be useful as a therapeutic agent if it lacked myelosuppressive activity.