Characterization of the baboon erythrocyte C3b-binding protein.
E from primates demonstrate type 1 CR (CR1) with binding specificities for C3b and C4b. In the present study we characterized the E C3b-binding protein of baboons. We showed that three out of four mouse mAb and one polyclonal antiserum, raised against human E CR1, cross-reacted with baboon E. In addition, one anti-human CR1 mAb (1B4) and a polyclonal anti-human CR1 inhibited the binding of C3b opsonized immune complexes to baboon E. Finally, a mAb to human CR1 (E11) recognized epitopes on E of a variety of nonhuman primates, including baboons. SDS-PAGE analysis of biochemically purified baboon E membrane fractions reactive with E11 demonstrated a 65-kDa protein as a major component. Affinity absorption and elution experiments verified this protein to be E11 reactive as well as a C3b binding protein. E surface radiolabeling, followed by C3i affinity purification, confirmed that this 65-kDa protein is the only C3b-binding protein present on the baboon E membrane. We postulate that the baboon E 65-kDa protein is the equivalent of the human E CR1. In addition, there appear to be antigenic similarities between the baboon E 65-kDa protein and the human E CR1.
Birmingham
D J
DJ
Department of Internal Medicine, Ohio State University, Columbus 43210.
Cosio
F G
FG
D000818:Animals; D000911:Antibodies, Monoclonal; D001666:Binding Sites, Antibody; D003179:Complement C3b / Q000378:metabolism*; D003429:Cross Reactions; D004910:Erythrocyte Membrane / Q000032:analysis / Q000378:metabolism*; D006801:Humans; D008970:Molecular Weight; D010215:Papio; D011951:Receptors, Complement / Q000276:immunology / Q000302:isolation & purification*; D017463:Receptors, Complement 3b
D000911:Antibodies, Monoclonal; D011951:Receptors, Complement; D017463:Receptors, Complement 3b; D003179:Complement C3b