Heat-killed macrophages (HK MØ) and/or semi-purified MØ membranes interfere with primary thymus-dependent but not thymus-independent in vitro immune responses. In addition, they can absorb out and render inactive the helper activity found in mixed lymphocyte culture supernatants which augments the primary in vitro response of normal spleen cells. They do not, however, inactivate the helper activity which augments the response of thymus-deprived spleen cells. Both the immunologic interference and the absorbing activity of the HK MØ are eliminated by treatments which inactivate or block Fc receptors. We suggest that HK MØ or their membranes can act as competitive antagonists for live MØ functions and in so doing block communication networks between T cell subclasses. Thus they can serve as useful probes both for studying some of the roles live MØ might play in mediating immunologic functions as well as dissecting out some of the many arcane T cell interactions which normally occur.

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This work was supported by Grants CA 08593, CA 14216, and AI 10497 from the National Institutes of Health and the United States Public Health Service.

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