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-gamma as a major component and IFN-alpha and -beta as minor ones, by acid stability tests and neutralization by antisera with defined specificities against alpha, beta, and gamma. 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-gamma production, indicating that T cells were the main IFN producers.