FIGURE 1.

CD300c delivers activating signals in RBL-2H3 cells. A, RBL-2H3 cells were stably transfected with 2×Myc-tagged forms of CD300c. Cell surface expression of CD300c molecules was checked by flow cytometry using anti-Myc9E10 mAb (dark gray histogram) or an isotypic mAb as a negative control (black histogram). B, RBL-2H3 transfectants were transiently transfected with 3×NFAT/AP1-Luciferase and TK-Renilla plasmids. Luciferase activity was measured after stimulation for 7 h with the indicated antibodies. Data were normalized and expressed as a percentage of luciferase activity considering IgE stimulation as the top threshold of activation. Duplicates were performed for all the stimulations. The result is representative of three independent experiments. C, RBL-2H3 transfectants were stimulated with the indicated antibodies to induce cell degranulation. Percentage of β-hexosaminidase release was assessed by incubating the supernatant with 4-nitrophenyl N-acetyl-β-d-glucosaminide substrate. Each assay was set up in triplicate. The result is a mean of three independent experiments (**, p ≤ 0.01). N.S., non-significant. Error bars represent standard deviation.