A novel biological function of macrophages associated with antigen discrimination properties

The ability of fresh or cultured subpopulation of adherent peritoneal exudate cells to perform discrete biological functions commonly associated with macrophages, namely antibody dependent cytotoxicity (ADCC) and phagocytosis, has been compared with the ability of the same cells to present TNP coupled to carbohydrate or protein carriers for a subsequent antibody response, or semi-allogeneic cells for T cell cytotoxic responses, in tissue culture. Data are presented to show that ADCC reactivity rapidly disappears on cultures of peritoneal cells, though phagocytic activity is more persistent throughout the 14 days of culture. When ADCC activity reappeared it was no longer restricted to those fractions active initially. Antigen handling of different TNP-protein conjugates was pronounced throughout the culture period and was not easily explained in terms of the ADCC/phagocytic activity of the macrophage subpopulation concerned. In contrast, however, antigen handling of carbohydrate antigens for presentation to T or B lymphocytes by the different macrophage populations varied during the culture period in fashions which were in some degree correlated with the phagocytic activity of the various cells but were also a function of the antigen under consideration. These data are interpreted in terms of a novel role for the macrophage in discrimination of carbohydrate antigens for presentation to lymphocytes.