Carcinoembryonic antigen binding proteins on elicited peritoneal macrophages

Carcinoembryonic antigen (CEA), a member of the immunoglobulin supergene family, is recognized by a specific 80-kd receptor on Kupffer cells and alveolar macrophages. Peritoneal macrophages were harvested from male Sprague-Dawley rats 72 h after intraperitoneal injection with thioglycolate broth and from unstimulated animals. The elicited peritoneal macrophages had a much greater capacity to endocytosed CEA than the cells isolated from unstimulated animals. They took up CEA in a concentration- and time-dependent manner. Cellular uptake was temperature and colchicine sensitive indicating internalization of CEA. The process was saturable and could be specifically inhibited by CEA and nonspecific crossreacting antigen (NCA), a member of the CEA supergene family. Two binding proteins of approximately 35 and 80 kd were isolated from the surface of the peritoneal macrophages by affinity chromatography on a CEA-Sepharose column. Using CEA coupled to sulfo-succininidyl-2-[p-azidosalicyl amide]-1,3'-dithiopropionate (SASD), a photoactivatable crosslinker, two binding proteins of 55 and 80 kd were identified on the surface of live peritoneal macrophages. The specificity of CEA endocytosis and binding proteins exhibited by the elicited peritoneal cells are similar to that previously reported for Kupffer cells and alveolar macrophages.