Subpopulation composition of T-helpers in the peripheral blood of persons chronically exposed to radiation in the long term

Abstract

Earlier, it has been convincingly established that exposure to ionizing radiation (IR) alters the T cell-mediated immunity in the long term. However, a search for papers describing the effect chronic exposure to radiation has on various subpopulations of T-helpers yielded no results. Therefore, we designed this study seeking to investigate the quantitative characteristics of various subpopulations of T-helpers in the peripheral blood of individuals chronically exposed to low-level radiation for a long period of time. The study involved 102 chronically exposed Techa Riverside residents (Russia) aged 60–87 years. The participants were divided into two groups, one comprised of exposed individuals with the average red bone marrow (RBM) irradiation dose of 567 ± 73 mGy, another, the control group, comprised of people with the irradiation dose below 70 mGy. With the help of flow cytometry, we identified the quantitative characteristics of T-helper subpopulations in the peripheral blood at various stages of their differentiation, as well as various T-helper subpopulations of central and effector memory. The study revealed no significant differences in the composition of T-helper subpopulations in the compared groups. We discovered a significant growth of the double positive follicular T-helper 17 subpopulation in the population of central memory T-helpers, which is associated with the increase of RBM (p = 0.04; S = 0.19), thymus and peripheral lymphoid organs (p = 0.03; S = 0.22) irradiation dose. In the group of exposed individuals, the number of naive T-helpers (p = 0.009) and double positive follicular T-helpers 17 in the TEM subpopulation (p = 0.04) was decreasing as the age of participants increased, and the number of effector memory T-helpers, on the contrary, increased with age (p = 0.04). We have not registered similar phenomena in the comparison group.