Augmentation of innate immunity by low-dose irradiation.
The effect of low-dose irradiation on the immune system was investigated in mice. When a 0.2 Gy dose of X-ray irradiation was administered every other day for a total of four times, the number of lymphocytes yielded by the liver, spleen and thymus decreased at the initial stage (around day 10). At this stage, NK cells, extrathymic T cells and NKT cells were found to be radioresistant. In other words, conventional lymphocytes were radiosensitive, even in the case of low-dose irradiation. However, the number of lymphocytes in all tested immune organs increased beyond the control level at the recovery stage (around day 28). Enumeration of the absolute number of lymphocyte subsets showed that the most prominently expanding populations were NK cells, extrathymic T cells and NKT cells, especially in the liver where primordial lymphocytes are primarily present. Functional and phenotypic activation of these populations also occurred at the recovery stage. It raised a possibility that an initial activation of macrophages by low-dose irradiation then mediated the present phenomenon. These results suggest that low-dose irradiation eventually has the potential to induce a hormesis effect on the immune system.
Ren
Hongwei
H
Department of Immunology, Niigata University School of Medicine, Niigata 951-8510, Japan.
Shen
Jiwei
J
Tomiyama-Miyaji
Chikako
C
Watanabe
Mayumi
M
Kainuma
Eisuke
E
Inoue
Masashi
M
Kuwano
Yuh
Y
Abo
Toru
T
D000818:Animals; D016207:Cytokines / Q000378:metabolism / Q000528:radiation effects; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005434:Flow Cytometry; D007113:Immunity, Innate / Q000528:radiation effects*; D008214:Lymphocytes / Q000528:radiation effects*; D008221:Lymphoid Tissue / Q000528:radiation effects*; D051379:Mice; D008810:Mice, Inbred C57BL; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors
D016207:Cytokines