LAD-2 cells were cultured as described (Kirshenbaum et al., 2003 (link); Radinger et al., 2010 ) in StemPro-34 medium containing 13 ml of StemPro-34 Nutrient Supplement and l-glutamine (2 mM) and penicillin (100 U/ml)/streptomycin (100 μg/ml; all from GIBCO, Grand Island, NY) with 100 ng/ml recombinant human SCF added (Peprotech, Rocky Hill, NJ). Half of the medium supplemented with SCF was changed every 7 d. HLMCs were obtained by lung resection for bronchial carcinoma and purified using immunoaffinity magnetic selection using anti-CD117 (BD Biosciences, San Jose, CA) as described (Sanmugalingam et al., 2000 (link)) and were cultured as described (Cruse et al., 2008 (link)). All human subjects gave written informed consent, and the study was approved by the Leicestershire Research Ethics Committee, United Kingdom. Human peripheral blood–derived mast cells were cultured from CD34+ progenitors as described (Radinger et al., 2010 ). The donors provided an informed consent, and cells were obtained under a protocol (NCT00001756) approved by the National Institute of Allergy and Infectious Diseases, National Institutes of Health Internal Review Board.