| Background:Radiation therapy plays important roles in tumor therapy. X-ray can damage normal tissues during radiotherapy including the immune system. So far, there is no effective treatment method for immune system injury induced by irradiation. In addition to the bone and calcium regulation, vitamin D is found to have a variety of functions, including the regulation of immune function[1], anti-tumor effects[2] and so on. But the immunoregulatory effects of vitamin D on irradiation induced immune dysfunction is not studied. In this study, we observed the effect of vitamin D on the immune function in mice with X-ray irradiation at different doses. These results could provide experimental basis for vitamin D use in cancer patients with radiotherapy for improving the immune function.Research method: In order to investigate the effect of vitamin D on the immune function in X-ray induced immunosuppression model, 40 ICR mice of 6-8 week old were randomly divided into 5 groups: control group, 2Gy and 5Gy irradiation groups, and vitamin D administration groups of 2Gy VD and 5Gy VD. The immunosuppression mouse model was established with 2Gy and 5Gy X-ray irradiation by AXESSE ELEKTA medical electron linear accelerator, and the dose rate was 600 c Gy/min. 1,25(OH)2D3(6 IU/g) was supplemented by intraperitoneal injection after 2Gy and 5Gy X-ray irradiation for 7 days. On the eighth day, blood samples were collected by enucleating the mouse eyeball and all mice were weighted and killed; Spleens and thymuses were isolated and weighted, and thymus and spleen indexes were calculated; HE staining was used to observe the morphology of thymus; The proliferation of spleen T lymphocyte induced by Con A was detected by MTT; The IL-2 secretion of spleen cells was detected by enzyme linked immunosorbent assay; The number of peripheral blood leukocytes, erythrocytes, platelets and lymphocytes in peripheral blood were detected by blood cell counter.Results: Compared with control group, the thymus index and spleen index of 2Gy and 5Gy group were significantly lower; Compared with 2Gy group, the spleen index of 5Gy group decreased significantly. but the thymus index was not significantly decreased; Compared with 2Gy group, the thymus and spleen indexes of 2Gy VD group were significantly increased; Compared with 5Gy group, thymus index of 5Gy VD group increased significantly, but the change of spleen index was not significant. Compared with control group, the cortical lymphocytes of thymus tissue of radiation group were decreased, and the thymus was atrophy. The damage was more severe in 5Gy group, but these indexs were better in vitamin D group. Compared with control group, the spleen T lymphocyte proliferation ability of 2Gy and 5Gy group decreased significantly; Compared with 2Gy group, the spleen T lymphocyte proliferation ability of 5Gy group decreased further. The supplementation with vitamin D could significantly improve the proliferation ability of spleen lymphocytes in 2Gy irradiated mice, but not in 5Gy irradiated mice. Compared with control group, the levels of IL-2 secretion of spleen cells was decreased in X-ray irradiated mice. The supplementation with vitamin D significantly increased the level of IL-2 secretion of spleen cells, especially in 5Gy irradiated mice. Compared with control group, in addition to red blood cells,the number of white blood cells, platelets, lymphocytes were significantly decreased in 2Gy group,the number were less in 5Gy group, compared with model group, vitamin D group the number of white blood cells, platelets and lymphocytes were increased, but not significantly.Conclusions:The inhibitory effect on the immune system is greater in higher dose of X-ray exposure. Supplementation with the immunoregulatory effects on X-ray irradiated mice was related with the radiation doses. Vitamin D(6 IU/g) could significantly improve the immune function of 2Gy X-ray irradiated mice. However, The immunoregulatory effects of vitamin D in 5Gy X-ray irradiated mice is weakened. |
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