Low dose, low dose rate photon radiation modifies leukocyte distribution and gene expression in CD4(+) T cells.
A better understanding of low dose radiation effects is needed to accurately estimate health risks. In this study, C57BL/6 mice were gamma-irradiated to total doses of 0, 0.01, 0.05, and 0.1 Gy ((57)Co; ~0.02 cGy/h). Subsets per group were euthanized at the end of irradiation (day 0) and on days 4 and 21 thereafter. Relative spleen mass and splenic white blood cell (WBC) counts, major leukocyte populations, and spontaneous DNA synthesis were consistently higher in the irradiated groups on day 0 compared to 0 Gy controls, although significance was not always obtained. In the spleen, all three major leukocyte types were significantly elevated on day 0 (P < 0.05). By day 21 post-irradiation the T, B, and natural killer (NK) cell counts, as well as CD4(+) T cells and CD4:CD8 T cell ratio, were low especially in the 0.01 Gy group. Although blood analyses showed no significant differences in leukocyte counts or red blood cell and platelet characteristics, the total T cells, CD4(+) T cells, and NK cells were increased by day 21 after 0.01 Gy (P < 0.05). Gene analysis of CD4(+) T cells negatively isolated from spleens on day 0 after 0.1 Gy showed significantly enhanced expression of Il27 and Tcfcp2, whereas Inha and Socs5 were down-regulated by 0.01 Gy and 0.1 Gy, respectively (P < 0.05). A trend for enhancement was noted in two additional genes (Il1r1 and Tbx21) in the 0.1 Gy group (P < 0.1). The data show that protracted low dose photons had dose- and time-dependent effects on CD4(+) T cells after whole-body exposure.
Department of Radiation Medicine, Loma Linda University and Medical Center, CA 92354, USA. dgridley@dominion.llumc.edu
Daila S
DS
Gridley
Asma
A
Rizvi
Xian
X
Luo-Owen
Adeola Y
AY
Makinde
Michael J
MJ
Pecaut
D000818:Animals; D001792:Blood Platelets / Q000378:metabolism; D015496:CD4-Positive T-Lymphocytes / Q000378:metabolism* / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D004912:Erythrocytes / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D007694:Killer Cells, Natural / Q000378:metabolism; D007962:Leukocytes / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008954:Models, Biological; D017785:Photons; D013154:Spleen / Q000378:metabolism; D013997:Time Factors