Similarities of murine gamma interferon and the lymphokine that renders macrophages cytotoxic.

Murine spleen lymphoid cells treated with insoluble (Sepharose bound) concanavalin A elaborate Gamma (immune) interferon (IFN-gamma) and macrophage activation factor (MAF) into the culture medium. Similarly, MAF is produced by T cells with other IFN-gamma inducers. MAF induces resting (noncytotoxic) macrophages to become tumoricidal. We have compared various physicochemical properties of MAF and INF-gamma, their neutralization by antibody to IFN-gamma, and their induction period. In these parameters, induction of antiviral activity was compared to induction of macrophage tumoricidal activity. All of the parameters studied have given results that demonstrate close similarity in the physical properties, molecular characteristics, and biological reactivities of the two lymphokines, and this similarity suggests that these two lymphokines reside in the same molecule. This conclusion would include that IFN-gamma, like IFN-alpha and IFN-beta, is capable of activating macrophages to become cytotoxic toward tumor cells.