Abstract
Genetic instability has been suggested as one of the causes for the development of late effects following radiation exposure, whereas human data are limited. Our recent study on lymphocyte bearing clonal chromosome aberrations in A-bomb survivors did not indicate the presence of the instability in vivo. In the present study, we examined if the instability is observable during in vitro propagation of clonally-derived peripheral T lymphocytes from A-bomb survivors using the same indicator for the in vivo study. One survivor (estimated dose of 1.15Gy, case 1), and one control subject (0 Gy, matched by age and sex, case 2) were studied. Blood T cells were clonally propagated in vitro using standard methods, and metaphases were prepared for multi-color FISH (M-FISH) analysis. One hundred cells were examined for each clonal cell population. We obtained 22 clonal cell populations from case 1 (8 populations with normal karyotype, 8 with identical aberrations derived from clonal cells in vivo, and 6 with different aberrations), and 18 populations from case 2 (all normal karyotype). In case 1, 27 additional aberrations (translocation and derivative chromosome) were found in total among 2,200 cells (1.2%), and the corresponding value in case 2 was 0.3% (6/1,800). Thus, the frequency of additional, sporadic aberrations in the exposed case was several times higher than that in the control subject. While the number of cases studied is limited, present results suggest the presence of chromosome instability among the clonally expanded lymphocytes in vitro from A-bomb survivors.
