Characterization of IL-2 receptor expression and function on murine macrophages

This study was designed to examine the expression and function of IL-2R on murine macrophages. We used a model system of murine macrophage cell lines (ANA-1 and GG2EE) that was established by infecting normal murine bone marrow-derived cells with the J2 (v-raf/v-myc) recombinant murine retrovirus. ANA-1 macrophages did not constitutively express detectable levels of mRNA for the p55, IL-2Rα. However, a brief exposure to IFN-γ was sufficient to induce IL-2Rα mRNA in ANA-1 macrophages. Flow cytometric analysis indicated that ANA-1 macrophages expressed low constitutive levels of IL-2Rα on their cell surface that were augmented after treatment of the cells with IFN-γ. Affinity binding and cross-linking of [¹²⁵I]IL-2 to ANA-1 macrophages demonstrated that IL-2Rα and the p70-75, IL-2Rβ were both present on ANA-1 macrophages constitutively. IFN-γ increased the expression of IL-2Rα on ANA-1 macrophages but did not increase the expression of IL-2Rβ on these macrophages. Although IL-2 alone did not induce the tumoricidal activity of ANA-1 macrophages, IL-2 acted synergistically with IFN-γ to induce macrophage tumoricidal activity. These data demonstrate the expression of IL-2R on murine macrophage cell lines and establish the role of IL-2 as a costimulator of macrophage-mediated tumoricidal activity.