The Effect Of 1,25‐dihydroxyvitamin D3 On Immunity In Mice Of Glucocorticoid Induced Immunosuppression Model

Objective: To explore the effects and mechanism of vitamin D on immune function in mice of glucocorticoid induced immunosuppression model.Method: Firstly, we divided all the mice were divided into five groups: control group, immunosuppression model group, and vitamin D supplementation supplementated groups including lower dose group, medium dose group and, higher dose group. And then the glucocorticoid immunosuppression mouse model was induced by intraperitoneal injection of dexamethasone(25mg/kg) for 3 days. At the same time the mice in control group and model group were injected with the same volume of aquae pro injectionsterilized watere as model group. Moreover, since the first day of this experiment, mice of in the three vitamin D supplementation supplementated groups were given intragastric administration with 1,25-dihydroxyvitamin D3 by intragastric administration for seven days at doses of 4 UI/g, 6 UI/g and 10 UI/g respetively. At the same time, mice of in the control and model groups were gavaged with same volume of aquae pro injectionewater. At the eighth day, all mice were weighted, blood was collected by extracting the eyeball using a tube with anticoagulant, EDTA, and then mice were killed by cervical dislocation. Spleens and thymuses were collected and weighted under sterile conditions, and indices for thymus and spleen were calculated. Spleen single cell suspension was prepared to for culture. Cells were stimulated After with c Concanavalin A(T lymphocyte activation) stimulation., T lymphocyte proliferation index was measured by MTT. Meanwhile we test the level of IL-2 of in the supernatant of the cultures by ELISA. Peripheral white blood cell number and classification were detected evaluated by an automatic blood cell analyzer. The percentages of T-lymphocyte subsets, B lymphocytes and NK cells were analyzed by a flow cytometer.Result: 1. In the mice of Group Model, the thymus index, spleen index, spleen lymphocyte proliferation index, the percentage of peripheral blood lymphocytes, IL-2 concentration in the culture of spleen lymphocyte, all of the percentages of lymphocyte subsets except for NK T lymphocyte, B lymphocyte and NK cells were significantly lower compared to control group. However, the percentage of NK in mice of Group Model was higher than the control group. 2. The thymus index of mice in three different vitamin D supplemented groups was significantly higher than that in mice of the model group. However there was no difference of spleen index between model group and vitmain D groups. 3. The spleen lymphocyte stimulation index in vitamin D medium dose group was significantly higher than that in model group, but lower than that in control group. Additionally, the lymphocyte stimulation index in vitamin D lower dose group and higher dose group were not different from that in the model group. 4. The level of IL-2 in cultures of vitamin D medium dose group mice was significantly higher compared to model group, but the levels of IL-2 in vitamin D low dose group and high dose group were not different from the model group. 5. Mice in vitamin D medium dose group had more lymphocytes in peripheral blood than mice in model group. Supplementation with vitamin D at medium or higher dose could significantly increase the number of WBC. 6. B lymphocytes in peripheral blood in the group of lower dose vitamin D were higher compared to the mice in model group, however, there was no different between vitamin D medium or higher dose groups and model group. 7. NK cells had a tendency to decrease in mice in the vitamin D medium dose group.The vitamin D higher dose group had a lower percentage of NK cells compared to that in mice of the model group. As the dose of vitamin D increasing, the percentage of NK cell were decreased. 8. The percentage of CD4~+ lymphocytes in the vitamin D lower dose group was lower than that in model group mice. What is more, with the dose of vitamin D increasing, the percentage of CD4~+ increased. And the percentage of CD8+ lymphocytes was significantly lower in the vitamin D lower dose group than model group. The ratio of CD4~+ and CD8+ increased with the dose of vitamin D increasing. Furthermore, mice in the vitamin D medium dose group and the high dose group had higher ratio of CD4~+ and CD8+ than model group, while the low dose group had no significant difference from model group.Conclusion:Vitamin D could improve the immunity of glucocorticoid induced immunosuppression immunosuppressant in mice. The immuoregulatory effects of vitamin D are dose dependent. The vitamin D at medium dose of vitamin D(6IU/g)has the highest best effects in ability of immune recovery. However, the ability of immune regulation of vitamin D would not increase further as the dose of vitamin D increasing. In addition, lower dose of Among three vitamin D dose groups, vitamin D at lower dose(4 IU/g) has the most important significant role effect in up-regulating the percentage of B lymphocytes compared to the other two vitamin D dose groups. In a word, vitamin D may have a role in improving the immune functon in the immunocompromised mice, through promoting T lymphocytes secrete cytokines such as IL-2.