The following reagents were purchased: Pipes, collagenase type la, hyaluronidase type I-S, N-FMLP, PAF (Sigma, Deisenhofen, Germany), anti-IgE (polyclonal from goat, Behring, Marburg, Germany), DNAse I (Boehringer, Mannheim, Germany), A23 187 (Calbiochem, Bad Soden, Germany), cimetidine (SmithKline Beecham, Munich, Germany), MEM/Earle's salts, FCS, IL-3 (Gibco, Berlin, Germany), histamine EIA (highly specific for histamine, sensitivity 0.2 nM; Immunotech, Hamburg, Germany), LTC, EIA (cross reaction with leukotriene (LT)D,: 46%, LTE,: 2% and LTB,: t0.01%, sensitivity 18 pg/ml, Cayman, Ann Arbor, MI, USA).Bufers. Pipes A (containing 0.1% HSA), Pipes EDTA (Pipes A containing 2% 0.1 M EDTA), and Pipes ACM (Pipes A containing 2 mM CaCI, and 0.5mM MgC1,) were used in all experiments at a pH of 7.40.Medium. In all experiments with mast cells, MEM containing 2% FCS, 1% penicillin and streptomycin, 1% glutamine, 2% MgSO,, and 10 pg/ml DNAse was used during the isolation process.