Cellular distribution of complement receptor type 4 (CR4): expression on human platelets.

摘要: Neutrophils have been shown to express a receptor for C3dg that is distinct from CR2 and termed complement type 4 (CR4). In the present study, other peripheral blood cell types were examined by indirect immunofluorescence flow cytometry presence of binding activity. Specific uptake occurred with neutrophils, platelets, B lymphocytes, but not eosinophils or T lymphocytes. Monocytes, contained within mixed population mononuclear cells also bound C3dg, whereas purified monocytes did not. Binding 125I-labeled glutaraldehyde-cross-linked platelets was saturable, an average 1940 molecules per platelet at saturation (n = 8), ranging in number 660 3930 bound. Activation thrombin consistently cause increase expression CR4 sites. 125I-C3dg competitively inhibited equally well unlabeled iC3b, approximately fourfold less C3b. The addition elutriated generated activity on these formation platelet-monocyte complexes. Thus, accounted initially observed partially monocytes. adherent property may enable them confer certain ability localize C3dg-coated immune complexes particles.