a a - OES NSA STSOT vo Rew TOSS OP Oa ee ay . aN reo * ., bbe het ak ‘ Ose at me AD arth Hah Mele le : sacha IMMUNOHEMATOLOGICAL ASPECTS OF FALLOUT RADIATION tion, which be involved isformation. ywed a de- ocytes with | correlated at the perespond was alder. Such ral decrease ymphocytes, ese cells to red. that a derelated with ar depletion ipacity gen- 1967). It results that ute basis a s capable of crease noted ts may also age-related n, however, ophils. The | with aging . to a cumu- and debility rum showed in and gloapted norms * be related vered blood hese people. ilso showed ith increasounced and in the IgG ire twice as the IgG im- 1967), it is mificant inling the in- ’L ratios in casians and ‘ase in older is and im- llese people . the literaGoldbloom, 56; Rafsky, Brill, Stern, & Corey, 1952); and is probably related to an accumulation of immunological reactions to infections. Parfentjev (1954) suggested that the increase in gammaglobulins he noted in aging dogs and chickens was related to continuous contact with infectious organ- isms resulting in hyperimmunization. Such a situation may be present in the Marshallese. The increased gammaglobulin levels would 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. Blumenthal and Berns (1964) state that while antibodies to exogenous antigens decrease with age there may be an age-related increase in gamma globulins, presumably containing antibodies to endogenous substances, On the other hand the changes may be of a compensatory nature. Perhaps in older people there is a greater conservation of immunoglobulins by some mechanisms which would decrease catabolism or excretion. Or there might be increased activity of those cells still capable of producing antibodies. Let us now consider the differences noted in the exposed population as compared with the unexposed. Radiation-induced aging is a poorly understood phenomenon. It is generally considered to be a late effect of radiation, a mani- festation of non-reparable injury, since such aging effects are usually not recognizable early. It seems likely that the relative depression of the peripheral blood elements noted in the exposed Marshallese is probably a- continuing manifestation of incomplete recovery of the hematopoietic injury originally sustained. The significant depression of the serum globulins and increase in serum albumins in the exposed population is a notable finding. The depression in the gamma andalpha globulins and the IgA moiety and to a lesser extent in the IgG group and the L light chains would seem to indicate a reduction in relative immunological capacity or at least lowered antibody reserves in the exposed people. The tendency for the depression of these moieties to be relatively greater in the older age groups may imply a radiation-induced aging effect. The lack of any differences in transformation of lymphocytes in response to PHA stimulation 35 in the exposed compared to the unexposed people cannot be readily explained in the light of the above findings. In spite of slight depression of blood elements and reduced serum globulin levels, the exposed Marshallese people, based on our observations over a 16-year period since the accident, have not been observed to have any recognizable impairment of immunological capacity based on the incidence or susceptibility to illness or diseases. If the serum protein changes are a recent development, then such deficiency may yet become apparent if the people are faced with a virulent antigenic challenge in the future. SUMMARY Age related and/or radiation-induced age effects on immunohematological criteria were tested in a Marshallese population of about 150 people, 50 of whom had been exposedto fallout radiation in 1954. In the unexposed group the following age-correlated changes were noted: \. decreasing percentage transformation of peripheral blood lymphocytes by phytohemagglutinin stimulation indicating decreasing immunological competence of lymphocytes; 2. significant increase in gammaglobulinreflected also in increases in IgG, IgA immunoglobulins and also increase of K light chains. These latter findings are believed to be associated with ageaccumulated effects of repeated exposures to infectious agents and perhaps to increased autoimmunereactions. In the irradiated population there were certain significant differences in the findings compared with the unexposed population which may indicate radiation effects. A relative depression of platelet and neutrophil levels of the peripheral blood was noted. Someslight degree of depression of peripheral blood elements has, however, been noted since exposure. Also noted were reduced gamma globulin levels (also IgG, IgA, and L light chains by immunodiffusion analysis), more pronounced in older age groups which mayindicate a radiation-induced aging effect. Evidence, however, for relative loss of immunological capacity in the exposed population has not been evident based on the incidence or severity of diseases compared with the unexposed population. The authors are grateful to Mr. K. Thompson of this laboratory for statistical assistance.