38 stimulation which was well correlated with in- creasing age. These results indicated that the percentage of lymphocytes that can respond to PHA 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 a decrease in lymphocytes well correlated with aging and compatible with cellular depletion and reduction in immunological capacity generally noted in the aged.48 These results indicate that with aging there is on an absolute basis a greater loss of PHA-committed lymphocytes than of noncommitted types. The slight decrease noted in the hematocrit and platelet levels may also be partof the phenomenonof 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 protein levels (both albumen and globulin) well above the usually accepted norms for Caucasians. This may be related in part to dehydration and lowered blood volumes, as mentioned earlier. The increase in gamma globulin levels in the aging Marshallese is consistent with manyreports in the literature.°0-53 Possibly the slightly lower albumen levels noted in the older Marshallese maybe related to lowered food intake. As expected from the serum electrophoretic data, the immunodiffusion studies showedincreasing immunoglobulin levels with increasing age (Figure 37). The most pronounced and most agecorrelated change was in the IgG group. Since the K light chains are twice as prevalent as the L light chains in the IgG immunoglobulins,*4 the significant increase in the K light chainsparalleling the increase in the IgG groupis not surprising. The K/L ratios in the Marshallese are similar to those in Caucasians®5 and showa slight butsignificant increase in older people. The increase in immunoglobulinsin the older Marshallese people is probably related to an accumulation of immunological reactions to infections. Parfentjev®® suggested that the increase in gammaglobulins he noted in aging dogs and 9006295 chickens wasrelated to continuous contact with infectious organisms resulting in hyperimmunization. Such a situation may be present in the Marshallese. The increased gammaglobulin levels seem to be incompatible with decreased immunological reactions in the aged. It has been suggested that the increased globulin levels may be partly related to the development of autoantibodies with age. Blumenthaland Berns*’ state that “. .. while antibodies to exogenousantigens decrease with age there may be an age-related increase in gamma globulins, presumably containing antibodiesto endogenous substances.” On the other hand the changes maybe of a compensatory nature. Perhaps in older people immunoglobulins are conserved by some mechanisms whichtend to decrease catabolism or excretion. Or the cells still capable of producing antibodies might be moreactive. If it had been possible to study age-related integrity of plasmacells and other lymphatic andreticuloendothelial tissues in these people, further light might have been shed on the problem.Finally, no attempt was madein the studies to separate “normal” older people from those with various morbid changes(if that is possible). Therefore someof the age-correlated changes may be associated with morbid processes. But are not these processes part of aging? It will be interesting in future studies of this population to see whether longitudinal changes on an individual basis agree with the cross-sectional results. . Interpretation of the differences between the exposed and unexposed populations is difficult be- ¢ cause radiation-induced agingis a poorly understood phenomenon.It is generally considered to } Die TLE aa The Marshallese in this study showed a decreasing transformation of lymphocytes with PHA be a late effect of radiation, a manifestation of nonreparable injury, since agingeffects are usually not recognizable early. The relative depression of the peripheral blood elements in the exposed Marshallese is probably a continuing manifestation of incomplete recovery from the hematopoietic injury originally sustained. Therefore, if such an effect is a part of the aging process,it has been. present since exposure, since continuing depression of blood elements has been noted on annualexaminations. Thesignificant depression of theserum globulins and increase in serum albumens in the exposed population is a notable finding. The depression in the gammaandalpha globulins and particularly in the IgA moiety and to lesser extent in the IgG group andthe L light chains