Thymus-specific T cell lineage–autonomous developmental blockade in Hq mice. (A) Representative analysis of thymocytes from 8–12-wk-old WT and Hq mice stained for CD4 and CD8, showing frequencies of cells in quadrants. Data are representative of three independent experiments. (B) Numbers of thymocyte subpopulations per thymus in WT and Hq mice, as mean ± SE (n = 4). *, P < 0.01. (C–F) Mixed bone marrow chimeric mice were constructed by giving CD45.1xCD45.2 F1 recipients WT CD45.1 bone marrow in a 1:1 ratio with CD45.2 WT or Hq marrow (as indicated). Chimeric mice were analyzed at 4–8 wk for the distribution of CD45 allotypes in various cell lineages in different tissues. Cells from chimeric mice were stained for donor CD45 allotypes and various lineage markers. Representative two-color plots are shown for peripheral blood cells stained for CD45 allotypes versus B220, CD11b, Gr-1, CD4, or CD8 (C), and bone marrow cells stained for CD45 allotypes versus B220 and Gr-1 and thymocytes stained for CD45 allotypes versus CD4 and CD8 (D). Frequencies of cells in each quadrant are indicated. Absolute numbers of lymph node CD4, CD8, B220, or CD11b cells (E) and of thymocyte DN, DP, CD4SP, and CD8SP subsets (F) of either CD45.1⁺ or CD45.2⁺ phenotype from the chimeric mice receiving either WT or Hq bone marrow as described. The groups shown are CD45.1 (WT donor) from chimeras given CD45.2 WT (CD45.1WT[WT]) or CD45.2 Hq (CD45.1WT[Hq]) marrow, and the CD45.2 cells from these chimeras (identified as CD45.2WT and CD45.2Hq). Data are shown as mean ± SE (n = 3). *, P < 0.01. Data are representative of five independent experiments.