Development of P1A-reactive T cells in RAG-2–deficient chimera mice reconstituted with a mixture of bone marrow cells from BALB/c and BALB/c P1CTL. Rag2^−/− BALB/c mice were given subcutaneous injections with either PBS or J558 tumor cells. Six days later, when the tumors were palpable, a mixture of T-depleted BALB/c P1CTL and WT BALB/c bone marrow cells (3:2) were injected intravenously in 2 doses at a 1-week interval. At 3 weeks after the second injection, when tumor rejection was observed in the periphery, the mice were killed and the T-cell subsets in the thymus were analyzed by 4-color flow cytometry using L^d:P1A dimer, and anti-CD3, -CD4, and -CD8. (A) Representative fluorescence-activated cell sorting (FACS) profiles of thymocytes from control (left panels) and tumor-bearing (right panels) mice are shown. The profiles of non-transgenic T cells are shown on the left of each group, whereas that of the transgenic T cells, as revealed by their specific binding to the P1A:L^d dimer or with anti–Vα8.3 TCR antibody, are shown on the right. (B) Summary of the T-cell subsets among polyclonal (top panel) and transgenic P1A-reactive T cells (bottom panel) in tumor-bearing and unchallenged mice. Graphs depict the mean ± SEM of 6 to 7 mice/group and are representative of 2 independent experiments.