Thymic progenitor B cells accumulate in the cortex and originate in the Foxn1^lacz mutant thymus.

<p><b>(A).</b> Immunofluorescence staining of sections from +/Z, Z/Z and Z/N thymus at day 30 for CD19 (red) and β5t (green) (top row), or CD19 (red) and K5 (green) (bottom row). <b>a,b.</b> Insets show digitally enlarged images of thymic B cells in the medulla in Z/Z (a) and subcapsular zone in Z/N mice (b). Scale bar = 0.1mm. <b>(B).</b> Analysis of CD45.1⁺ wild-type donor progenitor B cells (B220⁺CD19⁺ CD24⁺CD43^+/loIgM^-) in thymus, spleen, and BM at 21 days after transfer into sublethally irradiated adult CD45.2 +/Z and Z/N mice (top panels: PBS injection control; middle and bottom panels: CD45.1⁺ cells transferred into +/Z and Z/N mice). <b>(C).</b> Summary of CD45.1 cell numbers from the experiment in (B). Data are representative of two independent experiments, (PBS: n = 3, cells in +/Z: n = 2, in Z/N: n = 4). One-way ANOVA: **P <0.01, ***P <0.001. ns: not significant. Bars indicate means ± SEM.