title: Effect of BNU treatment on leukaemogenesis in lethally irradiated AKR mice restored with bone-marrow and spleen cells.
abstract: The leukaemogenic effect of N-butyl-N-nitrosourea (BNU) was studied in normal and thymectomized AKR mice which were lethally irradiated and restored with either bone-marrow (BM) or spleen cells from (AKR X AKR/T1ALD)F1 donors. In some instances T1ALD thymic cells were added to the restorative inoculum. It was possible to determine the origin of the leukemic cells by the metacentric marker chromosomes of T1ALD. The T- or B-cell characteristics were further ascertained by the cytotoxicity test for theta antigen and the EAC rosette test. All leukaemias whether thymic (TLS) or extra-thymic (ETL), developed from donor bone-marrow or spleen cells and never from the injected thymic cells. In non-thymectomized animals BNU increased the percentage of TLS and shortened their latency. Most of TLS which occurred after BNU treatment of BM-restored mice were theta-negative whereas the majority of TLS which occurred in controls and in spleen-restored animals were theta-positive. This suggests that during their maturation process BM-derived T precursors transit through a theta-negative compartment. This compartment does not reach a similar size during the maturation process of the spleen-derived precursors. Adding thymic cells to the restorative inoculum enhanced leukaemogenesis and suppressed theta-negative TLS in BM-restored mice. Thymectomized mice, restored either by BM or spleen, had a low incidence of ETL which was not significantly increased by BNU treatment except in the case of mice restored with spleen cells. The leukaemic cells of one ETL were theta-positive whereas all the other leukaemias had no detectable T or B marker. The percentage of ETL was higher in thymectomized mice treated with BNU alone than in those previously subjected to irradiation and restoration. These results strongly suggest that a theta-negative T precursor could be involved in extra-thymic leukaemogenesis but the possible involvement of a B precursor cannot be rule out unless experiments are carried out with specific markers of T- and B-cell sub-classes.
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology; D001854:Bone Marrow Cells; D016026:Bone Marrow Transplantation; D002462:Cell Membrane / Q000276:immunology; D003601:Cytotoxicity Tests, Immunologic; D000939:Epitopes; D005260:Female; D007942:Leukemia, Experimental / Q000139:chemically induced* / Q000235:genetics / Q000276:immunology; D007953:Leukemia, Radiation-Induced; D008297:Male; D051379:Mice; D008806:Mice, Inbred AKR; D009607:Nitrosourea Compounds; D013154:Spleen / Q000637:transplantation; D013934:Thymectomy; D013950:Thymus Gland / Q000276:immunology*
chemical_list: D000939:Epitopes; D009607:Nitrosourea Compounds