Late T Cell Deficiency in Victims of the Chernobyl Radiation Accident: Possible Mechanisms of Induction

Abstract

T cell number, serum concentrations of thymic hormones and anti-epithelial autoantibodies were studied in people affected at Chernobyl NPP. Group 1 took part in the clearing-up operation and had no clinical manifestations of acute radiation sickness. Group 2 worked at the NPP during the accident; they survived acute radiation sickness (degree I-II, subgroup 2a; degree III-IV, subgroup 2b). The total doses of external radiation were 0.1-0.5 Gy in group 1, up to 4 Gy in subgroup 2a and up to 9 Gy in subgroup 2b. Total T cell number, serum thymic activity and alpha 1-thymosin concentration were decreased in all groups of affected persons. CD8+ cell number decreased only in group 1; CD4+ cell number in subgroup 2b. A decrease in thymic hormone level was most prominent in subgroup 2b. The titres of anti-epithelial antibodies were increased in all groups of affected persons independently of radiation dose. The titres were higher in patients with subnormal levels of alpha 1-thymosin. It has been proposed that radiation alters the function of thymic epithelial cells by direct action and/or through indirect mechanisms including participation of autoantibodies. The observed complex of alterations is similar to that in the normal process of immunological ageing.

Chernobyl, 10 Years After: Health Consequences

“…It involved 1,356 subjects from five age brackets (children born in 1988, 1985, and 1980 and adults born in 1950 and 1930) nonrandomly selected in contaminated (>5 Ci/km 2 ) and uncontaminated villages. In 1991, the comparison of 71 healthy subjects with 30 liquidators close in age whose external exposure had varied between 0.1 and 0.5 Gy showed reduced CD8+ lymphocytes in the exposed subjects, results fairly consistent with those previously reported (64). The article furnishes few details about its sampling technique, however, and the sex ratio differed between the two groups.…”

Occupational exposure to ionizing radiation has no effect on T‐ and B‐cell total counts or percentages of helper, cytotoxic and activated T‐cell subsets in the peripheral circulation of male radiation workers

“…However, studies of the Japanese atomic-bomb survivors are restricted to groups who have received high acute doses (Akiyama 1995, Kusunoki et al 1998 and in whom significant cell killing may have compromised the proliferation and differentiation capacity of the haemopoietic cell system. In this respect it is notable that in the study of workers exposed at Chernobyl, a significant decrease in the CD4 z T-cell subset was observed in those exposed to w500 mSv, but not in those exposed to 100-500 mSv (Yarilin et al 1993). This evidence suggests that an effect on CD4 z helper T-cells is only evident at relatively high doses.…”

“…These effects are characterized by a decrease in circulating T-cell populations and an increase in the circulating B-cell populations in the atomic-bomb survivors (Akiyama 1995, Kusunoki et al 1998) and decreases in T-cell populations in the Chernobyl liquidators (Yarilin et al 1993). Thus, exposure to radiation appears to have altered the composition of peripheral blood lymphocyte populations, which can be detected many years after exposure.…”

“…The biological significance of these changes is currently unknown but effects of radiation on the immune system could have implications for the longterm health of exposed individuals. Populations studied to date include atomic-bomb survivors (Kusunoki et al 1988, 1998, Akiyama 1995, Chernobyl cleanup workers (Yarilin et al 1993), residents of buildings constructed with 60 Cocontaminated steel rods (Chang et al 1999) and occupationally exposed radiation workers (Tuschl et al 1995). Exposures in these groups vary in terms of radiation type, external and internal dose, fractionation and duration.…”

Irradiation accidentelle et reconstitution lymphocytaire T : données récentes et perspectives

“…L'étude des lymphocytes T des victimes de Hiroshima et de Nagasaki a permis de montrer l'existence de déficits fonctionnels des lymphocytes T pour les fonctions qui sont spécifiquement acquises au cours de la différenciation intrathymique (Akiyama et al, 1989;Akiyama, 1995). De même, une étude portant sur les liquidateurs de Tchernobyl a montré un déficit de la production d'une hormone produite par le thymus, l'al-thymosine (Yarilin et al, 1993 Cependant, ces études ne donnent que des informations indirectes sur les effets des rayonnements ionisants sur le thymus. La seule étude directe du thymus après irradiation a été faite chez des patients décédés après greffe de moelle osseuse.…”