Functions of T-cell subsets and their related cytokines in the pathological processes of autoimmune encephalomyelitic mice.

Objective: This study aims to observe the pathological changes of the brain and spinal cord in an experimental allergic encephalitis (EAE) mice model in the early onset, peak and remission periods of the disease, to detect the changes in the T-cell subsets and cytokine levels, to analyze the types of immune response and related principles in the different stages of the disease.

Methods: C57BL/6 mice were randomly divided into two groups: the EAE group (n = 18) and the control group (n = 18). C57BL/6 mice were immunized with myelin oligodendrocyte glycoprotein (MOG) 35-55 polypeptide/complete Freund's adjuvant (CFA) to establish the EAE mouse model. In the control group, the mice were treated with normal saline. The weights of the mice were recorded during the experiment. Peripheral blood was collected on the 0 day, 3rd day, 7th day, 14th day and 21st day after immunization, and the levels of T-cell subsets were detected by flow cytometry. The brain and spinal cord were taken on the 7th day (early onset), 18th day (peak) and 30th day (remission) after immunization. HE staining was used to observe the infiltration of inflammatory cells, and LFB staining was used to observe the loss of the myelin sheath. The immunohistochemical method was used to detect the T cells and B cell related proteins, and an ELISA assay was used to detect the changes of IL-4, IL-6, IL-10, IL-12, IL-17, IL-23, TNF-α, IFN-γ and TGF-β in mouse brain tissue. The interactions between the T cell subsets and cytokines, the types of immune responses of the EAE mice in different stages of the disease, and their related principles were analyzed.

Results: The symptoms of the EAE mice after treatment for 18 d were more severe than those at 7 d in the mice, while the symptoms were significantly relieved at 30 d. These findings coincide with the results of the weight measurement in mice. The immunohistochemical detection of T-cell and B-cell subset related factors showed that T cells accumulated in the brains of the EAE mice. In contrast, there was no obvious aggregation of B cells. The Th17 and Th2 levels in the T cell subsets in the EAE group were higher than those in the control group from the beginning of the treatment to the twenty-first day after the treatment. The level of Th1 in the EAE group was higher than it was in the control group on the seventh day after the treatment, and it was lower during the rest of the time than it was in the control group. There was no significant difference in the level of γδT between the control group and the EAE group. ELISA results showed that the cytokines in the EAE group were higher than they were in the control group on the seventh day after treatment, but the levels of IFN-γ, IL-12, TGF-β, and IL-23 in EAE group were lower than they were in the control group on the 18th day after the treatment. There was no significant difference in the levels of cytokines between the two groups on the 30th day after the treatment.

Conclusions: At the different disease stages of the EAE mice, the balance between Th1 and Th2 and the balance of Th17 differentiation changed. Th17 promoted the development of the disease, and Th2 was more effective in restoring health.