31 ment of cancer was 7 years in one case and 14 and ture aging in the exposed group that mightbeassociated with radiation exposure. During the past 3 years these studies have been extendedto include examination ofsomeaspects of the immunestatus in the exposed and unexposed 15 years in the other two. That the latent period may be longer is supported by Goolden’s observation of the developmentof thyroid cancer 40 vears after radiation exposure.38 It may be that we are just reachingthe critical period in the post-radiation observations. Marshallese populations which might be indica- tive of aging and/or radiation exposure. The studies reported here include measuringtransformation and replication of circulating lymphocytes from phytohemagglutinin (PHA) stimulation in SOMESTUDIES OF IMMUNOLOGICAL ASPECTS OF AGING AND FALLOUT RADIATION EXPOSURE culture, quantification of the various serum pro- teins by electrophoresis, immunodiffusion studies for immunoglobulin levels, and routine enumeration of peripheral blood elements. [a contrast to results of previous studies, some of the present tests showed differences between the exposed and unexposed groups that might be interpreted as radiation effects. Therefore the results on the unexposed population are treated separately here in order to determine the correlation ofthese criteria with aging in a normal Marshallese population. The results on the exposed group are comparéd with those on the unexposed group to evaluate possible radiation effects. Among the manv studies on the Rongelap people, the investigation of the possibility that radiation causes premature aging has been of continuing interest, particularly because such findings have been reported in irradiated animals.49 The 200 unexposed Marshallese people have served as an excellent comparison population for these studies since they are closely related and live in the same environment. For agingstudies, during physical examinations measurements were made on characteristics considered to be criteria of aging.49 Among these were skin elasticity and looseness and hair grayness; accommodation, visual acuity, and arcussenilis of the eyes; hearing loss; nerve and neuromuscularfunction, vibratory Materials and Methods sense, and handstrength; responseto light extinc- In Table 15 the numbers of subjects on whom the various tests were done arelisted according to age decades. tion test and rapid movement test; systolic blood pressure; and levels of blood cholesterol and body potassium (49K). Most of these criteria showed Lymphocyte Cultures. varying degrees of correlation with age and afforded a meansofarriving at a “biological age” Blood cultures were set up as follows. The buffy coat was separated from 5 ml of heparinized blood by sedimentation and centrifugat.on. The culture medium consisted of Eagle’s minimum essential medium supplemented score for each individual. However, none of the tests showed anysignificant indication of prema- Table 15 Numbers of Marshallese Subjects Tested in Various Studies (Since the results for males and females showed nosignificant difference, they were combined) Age group Lymphocyte transformation (1968) ——_—_-___—_-_~ Unexposed Exposed Serum proteins (1968) — Unexposed Exposed Immunoglobulins (1968) —_________—_— Unexposed Exposed 13-20 21-30 31-40 11 11 25 11 9 10 12 11 26 1] 10 10 6 9 9 41-50 19 4 19 4 11 61-70 12 3 12 3 12 51-60 15 71-80 9 Total 102 6 l 44 17 8 105 6 l 45 —_—_—_—-—— Unexposed Exposed 4 2 2 29 16 20 {5 7 7 2 11 8 2 11 3 16 98 11 3 7 | 65 Blood elements (1967) 3 6 5 1 46