Interferon inducers or semipurified preparations of interferon administered in vivo or in vitro enhance macrophage functions such as spreading on inert surfaces or phagocytic activity. In certain model systems cytotoxicity towards target cells may be also stimulated. Because of the relevance of macrophages to the clearance of particulate pollutants and to host responses to microorganisms and tumors, the mechanisms involved in the effects of interferon inducers and of interferon preparations on macrophages need to be further evaluated. In particular, more stringent evidence is required that the effects are indeed mediated by interferon. We propose in this application: 1) to obtain monoclonal antibodies to mouse viral (type I) interferon by the hybridoma methodology in order to acquire specific reagents able to functionally inactivate the interferon. Liposome entrapped interferon preparations will be used for immunization in order to increase the number of specific B cell precursors in the spleen; 2) to compare the features and requirements for in vitro phagocytic stimulation with those for the acquisition of the anti-viral state in macrophages. Specifically, to evaluate the role of priming with interferon and the effect of protein and RNA synthesis inhibitors on the acquisition and decay of the phagocytic enhancement induced by interferon preparations; 3) to examine the endocytic effect of interferon preparations on inflammatory or activated macrophages; and 4) to determine whether phagocytosis by other cells, such as macrophage-like lines, polymorphonuclear neutrophils or fibroblasts, is also affected by interferon preparations.