C4b and C3b are opsonins, which are able to bind covalently to glycoproteins on the target cell surface. Opsonization by C3b or C4b leads to engagement of complement receptors (CR1, CR3 or Cr4) on acceptor phagocytic cells, thus targeting foreign particles for phagocytosis [Bohnsack JF et al 1985].
C3b and C4b have been reported to facilitate a clearance of immune complexes (IC) which begins with covalent attachment of C3b or C4b to IC. C3b/C4b-coated immune complexes are loaded on erythrocytes via C1R and are transferred to phagocytes in the liver and spleen [Hakansson L et al 1982; Taylor RP et al 1991; Pascual M and Schifferli JA 1992; Emlen W et al 1992].
Håkansson, L, Hällgren, R, Venge, P
Emlen, W, Carl, V, Burdick, G
Pascual, M, Schifferli, JA
Taylor, RP, Pocanic, F, Reist, C, Wright, EL
Bohnsack, JF, O'Shea, JJ, Takahashi, T, Brown, EJ
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