DO HUMAN-LYMPHOCYTES EXPOSED TO THE FALLOUT OF THE CHERNOBYL ACCIDENTEXHIBIT AN ADAPTIVE RESPONSE .1. CHALLENGE WITH IONIZING-RADIATION

Several studies suggest that cells appear to become less susceptible t o the induction of radiation damage, and in particular of chromosome a nd chromatid aberrations in shea-term cultures of human lymphocytes, w hen a challenge exposure to ionizing radiation is preceded by a low 'a daptive' dose. Contradictory results have been reported on the conditi ons under which the phenomenon can be evidenced. In the present work, circulating lymphocytes of 13 children contaminated from the fallout a fter the Chernobyl accident were tested for their capability to exhibi t an adaptive response in experiments in which the challenge dose was administered to stimulated lymphocytes in the S-G(2) phase. Furthermor e, the possible influence of 3-aminobenzamide, an inhibitor of poly(AD P-ribose) polymerase, was also investigated. Our results indicate that , at least in the instance of the end-point here used (chromosome and chromatid aberrations, the former resulting possibly from the Cs burde n), human lymphocytes, chronically exposed to low doses from fallout, do not exhibit any decreased susceptibility to ionizing radiation. How ever, as reported in the accompanying paper, the same samples appear t o show an 'adaptive' response when exposed to a challenge treatment wi th bleomycin (B. Tedeschi et al., 1995, this issue).