Interferons are natural cytokines with a variety of biological effects including antiviral, untiproliferative, antifibrogenic and antianiogenic properties (Hiramatsu et al., 1995; Muriel 1996; Kim et al., 2000). Interferons inhibit transcription and
translation of a number of RNA and DNA viruses as well as the growth and preliferation of a variety of cells (Theocharis et al., 1997). Furthermore, interferons could alleviate fibrosis and inflammation (Mazzoran et aI., 1998). The two main members of interferon I family namely interferon alpha and beta have gained special value as they proved to be successful in treatment of chronic viral infections, rnyoproliferative disorders and autoimmune diseases, Interferon alpha is the only available effective treatment for chronic viral hepatitis C (Kaserer et al., 1998; Duchatelle et al.,1998). It is also used in chronic hepatitis B, chronic non A non B hepatitis and chronic delta hepatitis (Yoo et al., 1990; Kleiner et al., 1993; Manabe et al., 1993). Moreover, it is useful in reversing liver damage induced by biliary obstruction (Moreno & Muriel 1995). Through its irnmunomodulatory activity, interferons decrease the incidence of severity of precancerous lesions (Merle et al., 1997). It is also efficacious in treatment of pancreatic tumors. renal cell carcinoma. chronic
myelogeneous leukemia, hairy cell leukemia, cutaneous melanoma and polycythemia (Lamers 1990; Baer et aI., 1992; Toliou et al., 1996; Bose et aI., 1997; Elliot & Tefferi 1997; Otely & Zitelli 2000).
Despite of the variation in the etiology of the diseases treated by interferons and the different types of immune responses thought to be required 10 control them, interferon I is able to provide effective therapy. It is likely that interferon induced
marked changes in the immune status which depend on its ability to influence the differentiation of Band T lymphocytes and increase lymphocyte adhesion to endothelial cells by up-regulation of adhesion molecules (Steinger & Van Der Meide,1993). Among its other immunological effects, interferons provoked activation and proliferation of rnonocytes, rnacrophages, cytotoxic T cells and natural killer cells eliciting long lasting tumor specific immunity (Eguchi et at, 2003). These changes were accompanied by augmented expression of surface activation markers on the ef· fecter cells (Suzuki et aJ., 2002).