LETHALITY AND MUTAGENESIS OF B-LYMPHOCYTE PROGENITOR CELLS FOLLOWING EXPOSURE TO ALPHA-PARTICLES AND X-RAYS

B lymphocyte precursor cells are the target cells for the major subtyp e of paediatric cancer, acute lymphoblastic leukaemia. Using a murine IL-7-dependent clonogenic assay for normal B cell precursors as a mode l, we have investigated the sensitivity of these cells versus other no rmal and leukaemic haemopoietic cells to alpha-particle radiation. We find that B cell precursors are remarkably susceptible to the lethal e ffects of alpha-particles and have a very low probability of surviving a single alpha-track. B cell precursors are also very sensitive to th e lethal effects of low LET X-rays. The mutation frequency in a marker gene (HPRT) does not, however, appear to be greater in B cell precurs ors that survive X-radiation than in other haemopoietic cells.