Competitive repopulation advantage of WT versus WASP^— stem cells in WASP^— mice following transplantation. WASP^— mice received transplants of varying percentages of Ly5.1(WT) cells as follows: 10% (▵), 20% (○ and •), or 50% (♦), with the remainder of cells transplanted being Ly5.2(WASP^—) cells (top row). For control mixtures, WT (littermate) Ly5.2 bone marrow cells were substituted for WASP^— cells (bottom row). The mixture of 20% WT versus 80% WASP^— cells was performed in 2 sets of animals. Peripheral blood was obtained at the times indicated and analyzed by flow cytometry using a monoclonal antibody specific for the Ly5.1 epitope. T-cell marker: Thy 1.2. B-cell marker: B-220. Neutrophils were gated by forward versus side scatter. Monocytes were also gated by forward versus side scatter, with backgating to minimize lymphocyte (B220+ or Thy 1.2+) contamination. Each data point represents the mean and standard errors of data obtained from 4 to 6 animals.