RADIATION LEUKEMOGENESIS - QUANTITATIVE RELATIONSHIP BETWEEN PRE-LEUKEMIC CELLS IN THE THYMUS AND LYMPHOMA INDUCTION

Fractionated irradiation of C57BL/6 mice induces a population of pre-l eukemic (PL) cells that progress into mature thymic lymphomas after a latency of 4 to 6 months. Transfer of graded numbers of thymocytes fro m an irradiated mouse into recipient mice indicated that PL cells firs t appear in the thymus 6 weeks after irradiation. The initial proporti on of the thymic PL cells is greater than or equal to 10(-5) and their frequency continuously increases with time, reaching greater than or equal to 10(-3) 10 weeks after irradiation. The PL cell population tha t emerges early during the pre-malignant latency consists of pleioclon al T lymphocytes. However, within 4 weeks a dominant PL clone can be d etected which becomes the progenitor of a clonal lymphoma 9 to 15 week s later. These results suggest that radiation leukemogenesis involves continuous accumulation of pleioclonal PL cells in the thymus, one of which is then selected for further maturation into frank lymphoma. (C) 1994 Wiley-Liss, Inc.