Recent work from several laboratories has shown that murine gamma interferon induces the biosynthesis and cell surface expression of immune-associated (Ia) glycoprotein determinants on both normal and neoplastic mouse mononuclear phagocyte lineage cells. Experiments carried out by the principal investigator demonstrate that gamma interferon activates a murine macrophage tumor cell line, (P-388.D1), to release a second, noninterferon factor activity which, in turn, stimulates Ia expression on mouse macrophage tumor cells. The major goal of this research proposal is to test the hypothesis that gamma interferon regulates the positive expression of macrophage Ia determinants by stimulating the induction of a second group of Ia-inducing factors (IaIF) by the macrophage which subsequently control the cell surface expression of individual Ia subregion determinants. Thus, a variety of murine macrophage tumor cell lines and normal mononuclear phagocyte subpopulations will be cultured in vitro using different Ia induction procedures, and conditioned medium from these cells will be tested against neoplastic and normal Ia negative macrophage target cells for the ability to induce Ia expression. Quantitation of Ia induction will be carried out using direct and indirect immunofluorescence with anti-Ia monoclonal antibodies and flow cytometry analysis (FcM). Where active IaIF supernatants are found, they will be examined using standard biochemical analysis techniques in an effort to characterize the material and show if there are multiple IaIF activities which control the expression of discrete Ia subregion glycoproteins. Normal or neoplastic macrophages which are induced by IaIF activity for one or more Ia subregion antigens (i.e., I-A, I-E/C, or I-J), will be studied for functional activity as antigen-presenting cells in T-cell proliferation and activation assays using MHC-restricted, antigen-specific, continuous helper T-cell lines, or T hybridomas as effector cells. I-J-inducible macrophages will be tested as accessory cells in the induction of a primary in vitro burro red blood cell IgM response, and as antigen-presenting cells in the activation of third-order suppressor T cells (Ts 3) in the azobenzenearsonate (ABA) system. This study will provide basic information describing the mechanism by which gamma interferon may regulate the cell surface expression of individual Ia subregion antigens on phenotypically and functionally unique subsets of mononuclear phagocytes. (SR)
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