Jl. Williams et al., EFFECTS OF RADIATION ON SURVIVAL AND RECOVERY OF T-LYMPHOCYTE SUBSETSIN C3H HEN MICE/, Experimental hematology, 22(6), 1994, pp. 510-516
The aims of this study were to determine the radiosensitivities of mur
ine thymic and splenic CD4(+) and CD8(+) lymphocytes and to evaluate t
he regeneration of these cells in a model of radiation-induced hematop
oietic and immune suppression. CD4(+) and CD8(+) cells were quantitate
d using two-color flow-cytometric analysis. Cells obtained from C3H/He
N mice 24 hours after exposure to 0.25-8.0 Gy (0.4 Gy/min) Co-60 were
used to determine D-0 values. Thymic CD4(+) cells contained a radiosen
sitive subpopulation with a D-0 of 0.97 +/- 0.05 Gy and a radioresista
nt subpopulation that survived exposures up to 8.0 Gy. CD8(+) cells al
so contained a radiosensitive subpopulation with a D-0 of 1.24 +/- 0.0
5 Gy and a radioresistant subpopulation with a D-0 of 3.93 +/- 2.01 Gy
. Double-positive thymic CD4(+)/CD8(+) cells were uniformly radiosensi
tive, with a D-0 of 1.03 +/- 0.28 Gy. Multiple T lymphocyte subpopulat
ions based on radiosensitivity and CD4/CD8 antigen expression were als
o observed in the spleen. When mice were exposed to a sublethal 6.5-Gy
radiation dose and recovery of T lymphocyte subsets was monitored, th
e relative radioresistance of CD4(+) cells resulted in a selective enr
ichment of these cells among the surviving thymocytes and splenic lymp
hocytes. This relative enrichment of CD4(+) cells became even more pro
minent 7 days after irradiation, when atrophy of the organs was greate
st. Similar, although less dramatic, effects were observed for CD8(+)
cells. These studies demonstrate that (1) multiple T lymphocyte subpop
ulations can be identified based on radiosensitivity and CD4/CD8 antig
en expression; (2) both CD4(+) and CD8(+) cells contain radioresistant
subpopulations, with the CD4(+) subpopulation being more resistant th
an the CD8(+) subpopulation; and (3) although the number of radioresis
tant CD4(+) cells is quite small, they persist in increased proportion
s during the periods preceding and corresponding to postirradiation he
matopoietic recovery.