Analysis of cytokine production and apoptotic cells in tumours following intra-bone marrow–bone marrow transplantation (IBM-BMT) with or without adult thymus transplantation (ATT). (a) Spleen cells were intracytoplasmically stained with phycoerythrin-anti-interleukin (IL)-2, IL-4, IL-10 or interferon (IFN)-γ monoclonal antibodies (mAbs) to determine the per cent of IL-2-, IL-4- or IL-10-producing cells. Non-treatment, n = 4; IBM-BMT alone, n = 4; IBM-BMT + ATT, n = 4. *P < 0·05 compared with non-treatment; **P < 0·05 compared with non-treatment and IBM-BMT alone. (b) Representative findings for tumour cells with terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labelling (TUNEL) staining (×400). TUNEL-positive tumour cells were observed (arrows). Numbers of TUNEL+ cells after treatment with IBM-BMT with and without ATT were compared. Numbers of TUNEL-positive tumour cells were significantly elevated in the mice treated with IBM-BMT + ATT in comparison with those treated with IBM-BMT. IBM-BMT + ATT, n = 5; IBM-BMT alone, n = 5. Data are shown as mean ± standard deviation (SD). #P < 0·01.