Flow cytometric analysis (relative log fluorescence) of expression of Trk proteins in HMC-1 mast cells. HMC-1 cells were incubated with an anti-TrkA, anti-TrkB, or anti-TrkC antibody (as indicated in the figures), or with rabbit IgG (negative control, the thin line in the figures), and subsequently stained with fluorescein-conjugated goat antirabbit IgG and analyzed by flow cytometry. Data are representative of six separate experiments.