Negative selection is not perturbed in IL-7Rα Tg mice. (A) Thymocytes were counted after 4 days of in vitro FTOCs from wild-type (bars on left) and B1 Tg thymi (bars on right) that were taken at embryonic days 15 to 16. Where indicated, deletion was initiated with 10 mg/mL of anti-TCRβ antibody (H57-597) 24 hours before harvesting the cultures. Number of thymi in the study is shown on the top of each column. The bars indicate standard errors. (B) FTOC cellularity after 4 days in vitro culture of 15-day-old fetal thymi from 5CC7 (bars on left) or 5CC7 × B1 mice (bars on right) is shown. Where indicated, 0.1 μM MCC (88-103) peptide was added for the last 24 hours. The bars indicate standard errors. (C) Thymi from B1 thymi taken at day 15 were incubated in vitro for 4 days with or without 10 ng/mL of rhIL-7. Deletion was induced as described in panel A. The bars indicate standard deviations.