Supplemental Experimental Procedures

Measurement of Evans blue dye extravasation To quantify vascular leakage, ear biopsies were incubated in 0.3 ml formamide at 60 C for 4 days to extract EB from the tissue; absorption was measured at 620 nm. Counting of ear mast cells Mast cells per horizontal ear cartilage field length (mm) were counted. Stimulation of mast cells For stimulation of FLMCs and RBL-2H3 cells via Fcε receptors, cells were incubated with mouse anti-trinitrophenol (TNP) IgE (1 µg/ml, BD Biosciences) at 37oC for 2 hours, washed twice with PBS, and then incubated with TNP-34-BSA (bovine serum albumin; 50 ng/ml, BIORESEARCH TECHNOLOGIES) at 37oC for 1 or 6 hours in Tyrode’s buffer (130 mmol/L NaCl, 5 mmol/L KCl, 1.4 mmol/L CaCl2, 1 mmol/L MgCl2, 5.6 mmol/L glucose, 10 mmol/L HEPES, and 0.1 % BSA, PH 7.4). In some experiments, FLMCs were stimulated with A23187 (500 ng/ml, Sigma) at 37oC for 1 or 6 hours. β-hexosaminidase assay After stimulation of mast cells, the supernatant was collected and the cell pellets were lyse