Expression of FcγRI after exposure to G-CSF. FcγRI cell surface expression was evaluated by flow cytometry using FITC-conjugated rat antimouse FcγRI mAb (solid lines). (A-D) Cells transfected with WT G-CSF-R; (E-H) cells transfected with mutant G-CSF-R. In panels A, B, E, and F, cells were cultured for 30 minutes in the presence (B,F) or absence of G-CSF (A,E). In panels D and H cells were cultured for 3 days in the presence of G-CSF (100 ng/mL). Panels C and G depict the cells cultured in the absence of G-CSF for 3 days (+ 2.5% WEHI medium). Dotted lines indicate fluorescence of isotype-matched antimouse Ig-FITC–incubated cells.