FIG. 2.

Unirradiated bone marrow cells suppress the formation of radiation-induced thymic lymphoma through niche competition. Four-week-old B6.SJL (CD45.1) mice received one dose of 1.8 Gy TBI for four consecutive weeks. Bone marrow transplantation (BMT) was performed 6 h after final TBI. Each recipient was intravenously injected with 1 × 10⁷ bone marrow cells from mice on a CD45.2 background. Both male and female mice were used. Panel A: Lymphoma-free survival of irradiated mice that received bone marrow cells from either wild-type (WT) or Rag2^−/−; γc^−/− mice or did not receive bone marrow cells (No BMT). P = 0.0004 for WT BM vs. no BMT; P = 0.0071 for WT BM vs. Rag2^−/−; γc^−/− BM; P = 0.2553 for Rag2^−/−; γc^−/− BM vs. no BMT. P value was calculated using log-rank test. Panel B: Lymphoma-free survival of irradiated mice that received bone marrow cells from Rag2^−/−; γc^−/− or Rag2^−/− mice. These data are the summary of results from three independent experiments. P value was calculated using log-rank test. Panel C: Bone marrow cells and thymocytes were harvested to examine the repopulation of donor-derived cells by flow cytometry. Donor-derived repopulation was examined in LSK (Lineage⁻ Sca1⁺ cKit⁺) cells in the BM as well as DN2 (CD4⁻ CD8⁻ CD25⁺ CD44⁺), DN3 (CD4⁻ CD8⁻ CD25⁺ CD44⁻), DN4 (CD4⁻ CD8⁻ CD25⁻ CD44⁻), DP (CD4⁺ CD8⁺), CD8SP (CD8⁺) and CD4SP (CD4⁺) thymocytes. n = 5 mice for wild-type and n = 7 mice for Rag2^−/−. Data are presented as mean 6 SE. *P < 0.05 (two-tailed t test). Panel D. Lymphoma-free survival of irradiated mice that received bone marrow cells from Rag2^−/−; γc^−/− or IgM^−/− mice. P value was calculated by log-rank test.