hFcγRI conserves its properties as a high-affinity IgG receptor in transgenic mice. (A-B) Representative histogram plots of hFcγRI expression on indicated cell populations from blood or tissues of hFcγRI^tg 5KO mice (A) or blood of normal human donors (B). Two representative histogram plots from 2 different donors (#1 and #2) are represented for hFcγRI expression on neutrophils. (C) Histograms showing the expression of the respective FcγRs (FLAG) or the binding of indicated mouse monomeric IgG to FLAG-tagged FcγR⁺ CHO transfectants. Solid gray histograms represent the binding of secondary antibodies alone. (D) Histograms show the expression of the respective FcγRs (FLAG) or the binding of indicated IgG ICs (black line) or Ag alone (solid gray histograms) to FcγR⁺ CHO transfectants, as revealed by neutravidin staining. Note: the use of different secondary reagents to detect monomeric IgG (C) or IC (D) binding prevents comparing fluorescence intensities between histograms in panels C and D. (E-F) Real-time SPR sensorgrams and affinity constants were determined from SPR analysis. (E) Data correspond to the injection of 125nM hIgG1 (black) or mIgG2a (gray) onto immobilized hFcγRI. (F) Kinetic parameters determined from experiments presented in panel E and in supplemental Figure 1B. Data are representative of at least 2 independent experiments.