Purification and characterization of the pig analogue of human membrane cofactor protein (CD46/MCP).
A panel of mAbs were raised against pig lymphocytes. Seven mAbs immunoprecipitated a 50- to 60-kDa membrane-bound protein. This protein, termed JM4C8-Ag, was expressed on a wide variety of cells, including all circulating cells and cells of fibroblast, epithelial, and endothelial origin. The JM4C8-Ag was transmembrane-anchored and glycosylated. One of the Abs was used in immunoaffinity chromatography to isolate JM4C8-Ag from erythrocyte membranes. N-terminal amino acid analysis through the first 28 residues showed a 43% homology with the human complement regulatory molecule membrane cofactor protein (MCP; CD46). The purified protein had cofactor activity for factor I-mediated cleavage of human and pig C3b, confirming its identity as the pig analogue of human MCP. The purified protein also strongly inhibited lysis of rabbit erythrocytes by human and pig complement after activation of the classical or alternative pathway. This is the first report of a nonprimate analogue of MCP. The presence of a resident MCP on pig cells capable of acting as a cofactor in the control of human complement activation has consequences for the use of pig organs in xenotransplantation.
van den Berg
C W
CW
Department of Medical Biochemistry, University of Wales College of Medicine, Cardiff, United Kingdom.
Pérez de la Lastra
J M
JM
Llanes
D
D
Morgan
B P
BP
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000096:biosynthesis; D015703:Antigens, CD / Q000737:chemistry* / Q000276:immunology / Q000302:isolation & purification*; D003169:Complement Inactivator Proteins / Q000737:chemistry* / Q000302:isolation & purification* / Q000378:metabolism; D006031:Glycosylation; D006461:Hemolysis / Q000187:drug effects; D006801:Humans; D051916:Membrane Cofactor Protein; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000276:immunology / Q000302:isolation & purification*; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D011817:Rabbits; D013552:Swine
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; C497857:CD46 protein, human; D003169:Complement Inactivator Proteins; C497859:Mcp protein, mouse; D051916:Membrane Cofactor Protein; D008562:Membrane Glycoproteins