Immunological responses of aging Japanese A-bomb survivors

Immune response parameters were studied on 1341 A-bomb survivors residing in Hiroshima, Japan. Mononuclear cells were isolated from venous blood and tested for interleukin-2 production; lymphocytes were purified and tested for natural killer (NK) cell activity and interferon (IFN) production; and serum was tested for IFN and circulating immune complex (CIC) levels. Statistical analyses were performed for each type of assay using a linear models procedure including sex, age at the time of the bomb, radiation exposure, all the interaction variables, and the categorical variable day-of-assay in the model. The findings showed that (1) none of the immunologic variables were significantly affected by radiation exposure; (2) NK activity and CIC levels were positively associated with age; and (3) NK activity was on average higher for males than females. The data exemplify the difficulty in reaching firm conclusions concerning associations with radiation exposure when the dependent variable exhibits a large degree of interindividual and day-of-assay variability.