Fig. 4.

Loss of VAMP-8 does not affect histamine and TNF-α release from mast cells. Mast cells isolated from VAMP-8^−/− mice (and their wild-type littermates) were induced for secretion by IgE cross-linking by using 10 ng/ml DNP–BSA for 30 min (A–C) or with PMA/ionomycin for 15 min (D). The release of endogenous serotonin (A), histamine (B and D), or TNF-α (C) was determined and was expressed as a percentage of the total amount present in the supernatant as well as remaining in the cells. The data shown are means ± SEM of nine independent experiments (serotonin), five independent experiments (histamine), or three independent experiments (TNF-α). Asterisks indicate statistically significant differences between wild-type and VAMP-8-deficient mast cells (**, P < 0.005).