Natural cell-mediated cytotoxicity among A-bomb survivors residing in the United States

Natural cell-mediated cytotoxicity (NCMC) by lymphocytes from Japanese atomic bomb survivors now living in the United States was measured. Seventy-one individuals were exposed to an estimated '0.00' Gy ('0 rads') (S0 group) and 58 to greater than '0.00 Gy' (Ssub(+) group) at the time of the bomb. Of this 58,51 (88 per cent) received less than 0.50 Gy and 30 (52 per cent) received less than 0.10 Gy. NCMC was measured against 51Cr-labelled K562 target cells. Activity by lymphocytes from Ssub(+) group donors was significantly greater than that for the S0 group (p=0.028 by the stratified Wilcoxon rank-sum test). This difference between the Ssub(+) and S0 populations was detected 35 years after exposure to the bomb. It is therefore feasible and important to examine appropriate biologic parameters to elucidate the effects of low doses of radiation in humans. (author)