Appropriate doses of ionizing radiation facilitate the proliferation and anti-tumor effects of γδ T cells through ERK and p38MAPK pathways in vitro

Low dose ionizing radiation exhibits immunomodulatory properties. However, the impact of various doses of ionizing radiation on the antitumor responses of γδ T cells remains uncertain. The present study aimed to investigate the effects of different doses of ionizing radiation on the proliferation, cytotoxicity and related molecular mechanisms of γδ T cells in vitro. Human γδ T cells were exposed to radiation by X-ray with different doses. CCK-8 assay was used to measure cell proliferation. Cytotoxic activity was detected using LDH release assay. Cytokines IFN-γ and TNF-α were measured by ELISA. Flow analysis was performed to determine the expressions of perforin, granzyme B and CD107a in/on γδ T cells. Protein expression of Bax, Bcl-2, p-ERK1/2, and p-p38MAPK in γδ T cells were evaluated by western blotting analysis. The results showed that γδ T cells of the 0.08 Gy dose group exhibited the most pronounced proliferation. The antitumor cytotoxicity of γδ T cells and the levels of IFN-γ and TNF-α in the 2 Gy and 4 Gy groups were higher than those in the control group. Accordingly, the expression of perforin, granzyme B, and CD107a in these two groups was upregulated significantly. Protein analysis indicated that in the 0.08 Gy group, the expression of Bcl-2 and p-ERK1/2 was significantly upregulated, whereas Bax was downregulated. In the 2.00 Gy group, the expression of p-p38MAPK was notably upregulated. These findings indicate that appropriate doses of ionizing radiation may promote γδ T cell proliferation through the ERK pathway, and enhance the cytotoxic activity of γδ T cells by upregulating critical cytokines production and the expression of cytotoxic molecules through the p38MAPK pathway.