Interferon-Omega (IFN-?) coded by IFNW1 gene in human, is a number of the type I interferon family, which includes IFN-a, IFN-ß, and IFN-?. The IFNAR-1/IFNAR-2 receptor complex can help with the signal transduction, followed the antiviral or the antiproliferative actions. IFN-? is derived from IFN-a/ß and share 75% sequence with IFN-a. It has two intramolecular disulfide bonds which are crucial for activities. Mire-Sluis et al have described bioassays for IFN-a, IFN-ß, and IFN-? that exploit the ability of these factors to inhibit proliferation of TF-1 cells induced by GM-CSF. The bioassays can be used also with Epo and TF-1 cells, or Epo and Epo-transfected UT-7 cells.