DT treatment results in increased differentiation of DC precursors. (A) Competitive cotransfer approach to investigate splenic DC precursor activity in vivo. The DC precursor population was obtained from spleens of mice treated or not with DT for 2 days and MACS-depleted of CD11c⁺ cells. Five million cells from each donor were then cotransferred into irradiated recipient. Five days later, donor-derived DCs were quantified by flow cytometry based on CD45 congenic markers. (B) DCs predominantly derive from splenic precursors obtained from DC-depleted mice in cotransfer experiments. Representative flow cytometry data showing the relative percentages of cells from DT-treated (CD45.1) or untreated (CD45.1/.2) CD11c.DOG donor mice. (C) Bar diagram summarizing data shown in panel B from 4 individual mice. Results are expressed as mean percentage ± SEM. The experiment was repeated 3 times with comparable results. ***P < .005, Student t test. (D) CD45.1 and CD45.2 splenocytes have an equal capacity to generate DCs. The experiment was performed as in panels A to C except that DT treatment was omitted. (E) Bar diagram summarizing data shown in panel D from 3 individual mice. The experiment was repeated 2 times with comparable results. No statistically significant differences were observed (P = .109, Student t test).