B-LYMPHOCYTE AND MACROPHAGE EXPRESSION OF CARCINOEMBRYONIC ANTIGEN-RELATED ADHESION MOLECULES THAT SERVE AS RECEPTORS FOR MURINE CORONAVIRUS

The expression of carcinoembryonic antigen (CEA)-related glycoproteins that have been associated with intercellular adhesion and that serve as receptors for mouse hepatitis virus (MHV) was analyzed in cells fro m the immune system of BALB/c mice using immunolabeling and RNA polyme rase chain reaction amplification of receptor transcripts. These glyco proteins, which are called biliary glycoproteins,were highly expressed in B lymphocytes, including cells of the B-1a (CD5(+)) lineage, and i n macrophages, but were not detectable in resting T lymphocytes. Simil arly, murine cell lines of B cell and macrophage origin expressed mess enger RNA encoding CEA-related molecules, while the corresponding mRNA was only slightly detectable in a T cell line. These CEA-related cell adhesion glycoproteins were also expressed in endothelial cells. Ther efore, their specific interaction with their so far unknown ligand may be of functional importance in cellular interactions in the immune re sponse. Monoclonal antibody directed against these glycoproteins block ed MHV-A59 infection of the B cell-derived SP20 cell line. Thus, the f unctional receptors for MHV on B lymphocytes, like those on murine fib roblasts, are isoforms of CEA-related glycoproteins. Treatment of B ce lls with anti-receptor antibody also blocked B cell-mediated cytotoxic ity against MHV-A59-infected fibroblasts, indicating that this phenome non is mediated by interaction of viral attachment protein on the infe cted target cells with specific CEA-related receptor glycoproteins on the effector B cells.