Spontaneous production of interferon-gamma (IFN- γ) was shown in four (MT-1, MT-2, SMT-1 and HUT 102) of five human T-lymphoblastoid cell lines persistently infected with human T cell leukemea virus type I (MT-1, MT-2, SMT-1, HUT 102 and OKM-2). These four cell lines were not susceptible to the antivirus effect of IFN. In contrast, the multiplication of vesicular stomatitis virus (VSV) was restricted in the nonproducer cell line of IFN, OKM-2 cells by treatment of IFN- α or IFN- γ. Anti-proliferation effect of IFN w as investigated in producer cell line of IFN (MT-2 and SMT-1) and non-producer cell line of IFN (OKM-2). The growth of MT-2 cells was not affected by IFN- α or by IFN- γ. However, SMT-1 and OKM-2 cells were affected by treatment with externally added IFN-α
