Characterization of human IFN-gamma response using somatic cell hybrids of hematopoietic and nonhematopoietic origin.

A panel of 27 rodent-human somatic cell hybrids composed of cells of hematopoietic (nonadherent cells) and nonhematopoietic origin (adherent cells) was used to identify the chromosomes involved in the biological response to human IFN-gamma (Hu-IFN-gamma). We found that the stimulation of class-I histocompatibility antigen expression correlates with the presence of human chromosomes 6 and 21 in adherent cell hybrids, while human chromosome 6 alone is sufficient in nonadherent hybrids. Scatchard analysis of the binding of radiolabeled Hu-IFN-gamma to nonadherent cell hybrids gave a Kd value similar to that found on human cell lines. Induction of a reporter gene placed under the transcriptional control of the interferon responsive sequence (IRS) in adherent cell hybrids requires both chromosomes 6 and 21. The antiviral protection by Hu-IFN-gamma in adherent cell hybrids was reached at physiological doses (2 units/ml) when human chromosomes 6 and 21 were present, while higher doses of Hu-IFN-gamma (5000 units/ml) were required for hybrids lacking chromosome 21. Thus, we demonstrate that differences exit in the response to Hu-IFN-gamma depending on the origin of the cell type.