title: Mediation of CRP-dependent phagocytosis through mouse macrophage Fc-receptors.
abstract: The purified acute phase serum constituent, C-reactive protein (CRP), was examined for its ability to interact with mouse macrophage Fc-receptors when serving as an opsonin for C-polysaccharide (CPS)-coated erythrocytes (E.CPS). The ingestion of E.CPS-CRP by macrophage monolayers was dependent on the presence of CRP on the erythrocyte surface and on the treatment of the CRP-sensitized cells with human complement (C). The ingestion of E.CPS-CRP-C was inhibited by exposing the macrophages to either 2-deoxyglucose, a selective inhibitor of Fc-receptor activity, or to aggregated gamma-globulin. Inhibition was also brought about by plating macrophages on glass-bound immune complexes of BSA/anti-BSA (IgG) but not on complexes formed with the F(ab')2 fragment of the anti-BSA. Substrate-bound complexes of CPS-CRP selectively inhibited the uptake of IgG-coated E, EA(IgG); the inhibition was proportional to the concentration of CRP used to form the complex. The opsonin-independent ingestion of latex particles was not altered by these Fc-receptor blocking procedures. These findings coupled with the recent demonstration of a sequence homology between CRP and the CH3 domain of human IgG lead us to propose shared opsonic functions for antibody and CRP.
mesh_terms: D000818:Animals; D002097:C-Reactive Protein / Q000276:immunology*; D003165:Complement System Proteins / Q000378:metabolism; D003847:Deoxyglucose / Q000494:pharmacology; D007141:Immunoglobulin Fc Fragments; D008264:Macrophages / Q000276:immunology*; D051379:Mice; D008813:Mice, Inbred ICR; D009895:Opsonin Proteins; D010587:Phagocytosis
chemical_list: D007141:Immunoglobulin Fc Fragments; D009895:Opsonin Proteins; D003165:Complement System Proteins; D002097:C-Reactive Protein; D003847:Deoxyglucose