Human macrophages simultaneously express membrane-C1q and Fc-receptors for IgG.
Membrane C1q (mC1q) of macrophages (MPhi) is a precursor of the IgG-binding serum protein C1q. Thus, mC1q potentially provides one of several Fcgamma binding sites of mature MPhi and we analyzed whether simultaneous expression occurs of established receptors for IgG, FcgammaRI, II, and III, and mC1q during in vitro differentiation of MPhi. Using flow cytometry, immunoprecipitation combined with Western blotting and Northern blot analysis mC1q was hardly detected in freshly isolated blood monocytes, but increasingly in developing monocyte-derived MPhi. Laser scanning fluorescence microscopy confirmed the membrane localization of mC1q. Two-color-staining flow cytometry experiments indicated that mC1q and all three types of FcgammaRs are simultaneously expressed on mature monocyte-derived MPhi. A high correlation was found for the expression of mC1q and FcgammaRs, in particular FcgammaRII, but not mC1q and CD14, another marker of monocytes/MPhi.
Terheyden
Patrick
P
Institute of Medical Microbiology and Hygiene, Johannes-Gutenberg University of Mainz, 55101 Mainz, Germany.
Loos
Michael
M
Störkel
Stephan
S
Kaul
Marcus
M
D002454:Cell Differentiation; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D015922:Complement C1q / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism*; D047468:Immunoprecipitation; D008264:Macrophages / Q000166:cytology* / Q000378:metabolism*; D011485:Protein Binding; D011961:Receptors, Fc / Q000378:metabolism*
D007074:Immunoglobulin G; D011961:Receptors, Fc; D015922:Complement C1q