Decreases in percentages of naive CD4 and CD8 T cells and increases in percentages of memory CD8 T-cell subsets in the peripheral blood lymphocyte populations of A-bomb survivors

Yamaoka M, Kusunoki Y, Kasagi F, Hayashi T, Nakachi K, Kyoizumi S
Radiat Res 161(3):290-8, 2004

Summary

Our previous studies have revealed a clear dose-dependent decrease in the percentage of naive CD4 T cells that are phenotypically CD45RA⁺ in PBL among A-bomb survivors. However, whether there is a similar radiation effect on CD8 T cells has remained undetermined because of the unreliability of CD45 isoforms as markers of naive and memory subsets among the CD8 T-cell population. In the present study, we used double labeling with CD45RO and CD62L for reliable identification of naive and memory cell subsets in both CD4 and CD8 T-cell populations among 533 Hiroshima A-bomb survivors. Statistically significant dose-dependent decreases in the percentages of CD45RO^–/CD62L⁺ naive cells were found in the CD8 T-cell population as well as in the CD4 T-cell population. Furthermore, the percentages of CD45RO⁺/CD62L⁺ and CD45RO⁺/CD62L^– memory T cells were found to increase significantly with increasing radiation dose in the CD8 T-cell population but not in the CD4 T-cell population. These results suggest that the prior A-bomb exposure has induced long-lasting deficits in both naive CD4 and CD8 T-cell populations along with increased proportions of these particular subsets of the memory CD8 T-cell population.