© TAM, AAT ESN SR Lie ea heeds atebbedn nat a Vd Panatea ne 34 Jaane wo bes - CONARD, EMOISE, SCOTT, AND MAKAR values in the older age groups of the unexposed people. The increase in IgG moiety was most pronounced and showedsignificant correlation with age (r=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 no signifi- cant correlation with age (r=0.46). In the exposed population all of the immunoglobulins were depressed below levels of the unexposed group, the most pronounced depression was in the IgG and IgA moieties and in the L light chains. Discussion Although the role of the immune mechanisms in the aging process has never been clearly defined, it is generally agreed that such mechanisms are impaired in senescence. Ram (1967) in an excellent review of the subject pointed out that Lee it is well established that the capacity for immune responses increases during neonatal and juvenile life to a maximum in the young and adult animal, it remains constant for a time and then gradually decreases as the animal ages. The results of the present studies in the Marshallese people seem generally to support this thesis. The discussion which follows will first consider the results of the various tests in the unexposed population in terms of correlation with aging. The differences in the results in the exposed population will then be discussed in regard to radiation-induced effects. In regard to aging effects the unexposed population it is quite obvious from the various graphs that even in the tests showing changes more closely correlated with aging, changes are maximum by middle years (usually in the 40- to 50-age group), and there is little or no change, or in some cases a slight reduction, after middle age. The reason for this is not apparent. The response of lymphocytes to PHA stimulation in peripheral blood cultures was tested because of the active role of the lymphocyte in maintaining immunological integrity. The exact mechanism of action of the mitogen is unknown. “OAT Se: BERGEES Conard and Demoise (1970), using autoradiographic and subcellular fractionation techniques, showed that a tritiated PHA was localized largely in the cytoplasm of trans- formed lymphocytes, with the greatest concen- tration in the mitochondrial fraction, which suggested that such organelles may be involved in initiation of lymphocyte transformation. The Marshallese in this study showed a decreasing transformation of lymphocytes with PHA stimulation which was well correlated with increasing age, indicating that the percentage of lymphocytes that can respond was reduced as the Marshallese grew older. Such a finding appears to indicate a general decrease in immunological capacity of the lymphocytes, assuming that the response of these cells to specific antigens is similarly impaired. Peripheral blood counts showed that a decrease in lymphocytes was well correlated with aging and compatible with cellular depletion and reduction in immunological capacity generally noted in the aged (Ram, 1967). It would appear, therefore, from these results that with aging there is on an absolute basis a greater relative loss of lymphocytes capable of responding to PHA. Theslight decrease noted in the hematocrit and platelet levels may also be part of the phenomenon of age-related cellular depletion. Such reduction, however, was not noted in the case of neutrophils. The increasing sedimentation rate noted with aging in the Marshallese could be related to a cumulative effect of chronic infections and debility in the older age groups. Electrophoretic studies of the serum showed serum protein levels (both albumin and globulin) well above the usually accepted norms for Caucasians. This finding may be related in part to dehydration and lowered blood volumes which we have noted in these people. The immunodiffusion studies also showed increasing immunoglobulin levels with increasing age (Fig. 4). The most pronounced and most age-correlated change was in the IgG group. Since the K light chains are twice as prevalent as the L light chains in the IgG immunoglobulins (Ritzman & Levin, 1967), it is not surprising that there was a significant increase in the K light chains paralleling the increase in the IgG group. The K/L ratios in the Marshallese are similar to Caucasians and show slight but insignificant increase in older people. The increased gamma globulins and immunoglobulins in the older Marshallese people is consistent with many reports in the literature (Das & Bhattacharya, 1961, Goldbloom, 1955; Karel, Wilder, & Beber, 1956; Rafsky,