IgE, but not SF, requires the entry of extracellular calcium to trigger BMMC adhesion to FN. (A) Adhesion of normal BMMCs to FN in response to medium alone (C), 1 μg/mL IgE, or 5 ng/mL SF for 30 minutes with (□) or without (▪) the addition of 1.8 mM CaCl2. (B) Intracellular calcium measurements in BMMCs stimulated with 5 μg/mL IgE (thin solid line; left panel) or 50 ng/mL SF (thin solid line; right panel) alone, or in the presence of 50 μM 2-APB (dashed line) or 5 mM EGTA (thick solid line). The 2-APB was pre-incubated with the cells for 30 minutes, whereas the EGTA was added immediately prior to the addition of IgE or SF at 100 seconds (↓). (C) Adhesion of BMMCs to FN in response to 1 μg/mL IgE or 5 ng/mL SF for 30 minutes in the presence of vehicle control (□), 25 μM (▪), or 50 μM (▨) 2-APB added 30 minutes prior to stimulation. The background adhesion (6%) was subtracted. Adhesion was significantly (P < .05) different between IgE- and IgE + 2-APB–stimulated, but not SF- and SF + 2-APB–stimulated samples. Results shown are the mean ± SEM of triplicate determinations. Similar results were obtained in 3 (A), 3 (B), and 3 (C) separate experiments.
