Characterization of the baboon erythrocyte C3b-binding protein

D. J. Birmingham, F. G. Cosio

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)3140-3144
Number of pages5
JournalJournal of Immunology
Issue number9
StatePublished - 1989

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology


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