Interferon Production in Mixed Cultures of Mouse Spleen Cells and Tumor Cells: IFN-Gamma as the Main Component

Interferon (IFN) production in mixed cultures of mouse spleen cells and tumor cells was investigated, mainly using mouse myeloid leukemic cells, M1, and spleen cells from syngeneic SL mice. Spleen cells from other mouse strains (C57BL/6, BALB/c nude and C57BL/6 beige) and other tumor cells (L929 and YAC-1) were similarly effective for IFN production, but mouse mammary carcinoma FM3A cells were not. As the IFN-inducing stimulus, mycoplasma contaminating the tumor cells, or endogenous retrovirus in them, may possibly be involved. The type of IFN produced was identified as IFN-γ as a major component and IFN-α and -β as minor ones, by acid stability tests and neutralization by antisera with defined specificities against α, β, and γ. Depletion of natural killer cells from spleen cells did not appreciably affect IFN production, but depletion of Thy 1.2 antigen-bearing cells greatly reduced IFN-γ production, indicating that T cells were the main IFN producers.