Late Effects of Radiation on the Human Immune System: An Overview of Immune Response among the Atomic-bomb Survivors

Abstract

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 (⩾ 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) αβ⁺ 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 (1954–67), 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.