Flow cytometric analysis of thymocytes from recipients of TβRII^-/- or TβRII^+/- bone marrow cells at 3 weeks after transplantation. (A) Left panels show thymocytes stained to detect the cell surface antigens CD4 and CD8. Right panels show staining for CD25⁺ and CD44⁺ cells among the CD4^-CD8^- double-negative (DN) fraction. All cells were in addition stained and gated for the marker of donor cells, Ly5.2. The percentage of cells occupying each quadrant is indicated. (B) Mean percentage values of the subpopulations described in panel A. (▪) TβRII^-/- (n = 8); (▦)TβRII^+/- controls (n = 6). Results are expressed as mean ± SDs.