T cells of atomic bomb survivors respond poorly to stimulation by Staphylococcus aureus toxins in vitro: Does this stem from their peripheral lymphocyte populations having a diminished naive CD4 T-cell content?

Kusunoki Y, Yamaoka M, Kasagi F, Hayashi T, Koyama K, Kodama K, MacPhee DG, Kyoizumi S
Radiat Res158(6):715-24, 2002

Summary

We found previously that the peripheral CD4 T-cell populations of heavily exposed A-bomb survivors contained fewer naive T cells than we detected in the corresponding unexposed controls. To determine whether this demonstrable impairment of the CD4 T-cell immunity of A-bomb survivors was likely to affect the responsiveness of their immune systems to infection by common pathogens, we tested the T cells of 723 survivors for their ability to proliferate in vitro after a challenge by each of the Staphylococcus aureus toxins SEB, SEC-2, SEC3, SEE and TSST-1. The results presented here reveal that the proliferative responses of T cells of A-bomb survivors became progressively weaker as the radiation dose increased and did so in a manner that correlated well with the decreasing CD45RA-positive (naive) [but not CD45RA-negative (memory)] CD4 T-cell percentages that we found in their peripheral blood lymphocyte (PBL) populations. We also noted that the T cells of survivors with a history of myocardial infarction tended to respond poorly to several (or even all) of the S. aureus toxins, and that these same individuals had proportionally fewer CD45RA-positive (naive) CD4 T cells in their PBL populations than we detected in survivors with no myocardial infarction in their history. Taken together, these results clearly indicate that A-bomb irradiation led to an impairment of the ability of exposed individuals to maintain their naive T-cell pools. This may explain why A-bomb survivors tend to respond poorly to toxins encoded by the common pathogenic bacterium S. aureus.