Kinetics of donor T-cell chimerism. Peripheral blood was obtained at various time points after stem cell transplantation. Peripheral blood was then stained with monoclonal antibodies and the red blood cells were lysed. The stained whole-blood samples were then analyzed by flow cytometry. T-cell subsets and B cells were gated based on their expression of CD4, CD8, and B220 molecules. Myeloid cells were gated based on forward and side scatters (the gate was confirmed using anti-CD45, anti-CD11b, and anti-Gr-1 in the preliminary studies). The donor cells were determined by anti-H2D^b antibody in allogeneic T-cell-depleted bone marrow recipients or by anti-CD45.1 antibody in congenic stem cell recipients. The values (mean + SD) represent the results from 4 to 10 animals per group per time point. Allogeneic TCD BM recipients: P < .05 between groups at all time points (CD4⁺); for CD8⁺, P < .05 except on day +28 (P = .09), day +42 (P = .08), and day +56 (P = .08). Congenic TCD BM recipients: except between 8 × 10⁵ and 4 × 10⁶, P < .05 in both CD4⁺ and CD8⁺ cells. Congenic KTLS recipients: for CD4⁺, except on day +100 (P < .05, 1000 KTLS vs 5000 KTLS), P < .05 in at least 2 of the following comparisons: 400 KTLS versus 1000 KTLS, 400 KTLS versus 5000 KTLS, and 1000 KTLS versus 5000 KTLS; for CD8⁺, P < .05 in at least 2 of the following comparisons: 400 KTLS versus 1000 KTLS, 400 KTLS versus 5000 KTLS, and 1000 KTLS versus 5000 KTLS. The percentages of donor cells in B cells and myeloid cells were more than 95% in all groups at all time points tested. TCD BM indicates T-cell-depleted bone marrow; KTLS, c-Kit⁺Thy1.1^lowLin^-/lowSca-1⁺ hematopoietic stem cells.