Failure of BMP4 antagonists to suppress activity of FGF7. E15 FTOC was cultured for 7 days with FGF7 in the presence or absence of BMP4 inhibitor. (A) Representative FACS dot plots of CD44/CD25 (upper panels) and CD4/CD8 (lower panels) expression by thymocytes from untreated (left), FGF7 only–treated (middle), and FGF7 plus Noggin–treated (right) FTOC. R6, R7, and R8 denote DN1, DN2, and DN3 subpopulations, respectively. (B) Bars represent relative changes in total DN, DN1, and DN3 subpopulations in control, FGF7-treated, and FGF7 plus BMP4 inhibitor–treated versus untreated cultures in a total of 4 experiments. Differences with BMP4 inhibitor addition were not significant. (C) Bars represent relative changes in total cell number per lobe in these cultures in a total of 4 experiments. Differences with BMP4 inhibitor addition were not significant. Error bars indicate mean ± SD.