LATE EFFECTS OF RADIATION ON THE HUMAN IMMUNE-SYSTEM - AN OVERVIEW OF IMMUNE-RESPONSE AMONG THE ATOMIC-BOMB SURVIVORS

The studies of the late effects of atomic-bomb (A-bomb) radiation on the immune system were started about 20 years after the bombings in 1945. The most remarkable late effects of radiation are the functional and quantitative abnormalities of T and B cells in survivors exposed to high doses (greater than or equal to 1.0 Gy). Abnormalities of T-cell immunity include (1) a decreased proportion of CD3(+) T cells in peripheral blood lymphocytes, particularly the proportion of CD4(+)CD45RA(+) naive T cells (study period 1987-91); (2) an increased frequency of CD4(-) and CD8(-) (double negative) alpha beta(+) T cells (1987-91); and (3) functional defects in T-cell responses to mitogens and alloantigens (1974-85). B-cell abnormalities include: (1) a significant increase in the proportion of B cells among peripheral lymphocytes (1987-91); (2) an increase in serum immunoglobulin A levels in females and immunoglobulin M and the incidence of rheumatoid factor in both sexes (1987-89); and (3) an increased level of anti-Epstein-Barr virus antibody titer (1987-90). In contrast, suggestive (0.05 < p < 0.1) or not significant (p > 0.1) dose effects were observed for the number and function of natural killer cells (1983-91), and benign monoclonal gammopathy (1979-87). In addition, studies initiated sooner after the bombing such as the incidence of autoimmune diseases (1958-87), systemic bacterial infections (1951-67), and granulocyte functions (1947-79) also show little dose-effects. Thus, A-bomb radiation induced the alteration of the balance/interaction between the T- and B-cell subsets-specifically a decrease in the T-cell population and an increase in the B-cell population in the periphery.