37 globulin cantly in older people. Alpha andbeta gh the thou levels tended to show some increase min Albu t. correlation with age was notsignifican le. peop r olde levels tended to decrease slightly in s level ein Pronounced differences in serum prot lbu Thea on. were noted in the exposed populati men levels were significantly higher and the glob unex the in ulin levels significantly lower than posed group. Alpha1, alpha 2, and gammaglobulins showed the most pronounced depression in the exposed group (Table 16). Serum proteins, par- eMa Re bretonIS ie igi ticularly gamma globulins, showed greatest defi- 80 cits in the older exposed age groups. The results of the immunodiffusion studies are shown in Table 16 and in Figure 37. Parallel to the increase in serum gammaglobulin levels, the immunoglobulins showed increasing values in the older age groups of the unexposed people. The increase in IgG moiety was most pronounced and showed significant correlation with age (7 =0.78). The increase in the other immunoglobulins did not show a high correlation with age. The increase in the K light chains was highly correlated with age (r =0.96). Higher K/L ratios were noted in the older people though there was nosignificant correlation with age (r=0.41). In the exposed population all the immunoglobulins were depressed below levels of the unexposed group, the most pronounced depression being in the IgG and IgA moieties andin the L light chains. Discussion Thoughthe role of immune mechanismsin the aging process has never been clearly defined, it is generally agreed that such mechanisms are impaired in senescence. Ram48 pointed out that “. ++ it is well established that the capacity for immune responses increases during neonatal and Juvenile life to a maximum in the young adult animal, it remains constant for a time and then gradually decreases as the animalages.” Theresults of the present studies in the Marshallese people seem generally to support this thesis. In connection with the results of these studies, it should be pointed out that the Marshallese people understudy are notstrictly comparable with a population in the United States because of certain environmental andracial differences. 80 lesions, and intestinal parasites. Therefore it is not surprising that they have elevated gammaglobulin levels. The A/G ratio is reduced or reversed in most of the people. The serum protein levels are generally elevated, which may in part be related to dehydration associated with a tropical environment where dependence for wateris on rainfall which is scant at certain seasons. The specific gravity of the urine is frequently high, and reduced red cell and blood volume havebeen found. In spite of these factors the present studies should provide valid comparisons of the exposed and unexposed Marshallese populations, since both groups are generally exposed to the same environmental factors, and studies of genetically inherited characteristics show them to be a relative homogenous population. These studies are believed to test the immunological status of the individuals to some degree, although interpretation of someof the resultsis not readily apparent. The results of the various tests for the unexposed population are discussed below in termsof correlation with aging. The differences in the results for the exposed population are then discussed with regard to radiation-induced effects. In the unexposed comparison populationit is obvious from the various graphsthat, even in the tests showing changes more closely correlated with aging, the changes are maximum bythe middle years (usually in the 40 to 50 age group) with little or no increase, or in some cases even slight reduction, after middle age. The reasonforthis is not apparent. The response of lymphocytes to PHA stimulation in peripheral blood cultures was tested be- cause of the active role of the lymphocyte in maintaining immunologicalintegrity. PHAis generally believed to evoke a nonspecific blastogenic response in such cultures, since many more lymphocytes are transformed andproliferate with this agent than with specific antigens (such as tuberculin, tetanus, thyroid, pertussis, etc.). It is con- troversial whether or not PHAin this situation in- duces antibody formation. The exact mechanism As is generally true throughout Micronesia, even of action of the mitogen is unknown. Conard and Demoise,*? using autoradiographic and subcellular fractionation techniques, showed thata triti_ated PHA waslocalized largely in the cytoplasm of transformed lymphocytes, with the greatest people are in, to frequent infections such as gastroenteritis, upper respiratory infections, skin suggested that such organelles may be involved in initiation of lymphocyte transformation. though livirt\¥g:andards have been improving, the eviation. 5006294 concentration in the mitochondrialfraction, which