Description
IFNs are a large family of proteins having antiviral, antiproliferative, and immunomodulatory effects, and are divided into two major classes, type I and type II, based on differences in receptor binding and nucleotide sequence. Type I IFNs consist of IFN alpha, beta, tau, and omega and bind to the type I IFN receptor, whereas IFN-gamma is the only type II IFN and is specific for the type II IFN receptor. Human IFN-omega, was identified by three independent groups in 1985 and is structurally related to IFN-alpha and -beta. Both human IFN-omega and IFN-alpha are produced by virally induced leukocytes and have similar antiviral activities on human cell lines, and a sizeable proportion (at least 1%) of the total antiviral activity of leukocyte IFN is contributed by IFN-omegal. Also, it was reported that IFN-omega could inhibit the growth of human tumors in vivo