Expression Of Costimulatory Molecules PD-L1 In Experimental Allergic Encephalomyelitis

Background and Objective:Multiple sclerosis (MS) is an antigen- specific CD4 +Th1 cells mediated inflammatory demyelinating autoimmune disorder in the CNS. Programmed death ligand-1 (PD-L1) is a new member of the B7 family. PD-L1 regulates immune responses by interaction with programmed death receptor-1 (PD-1), an inhibitory co-stimulatory receptor induced on activated T, B and myeloid cells. Experimental Allergic Encephalomyelitis (EAE) is a T cell–dependent disease model used to investigate the pathophysiology of multiple sclerosis because its clinical cymptoms and pathology are similar with multiple sclerosis.To evaluate the role of PD-L1 in EAE and MS, we successfully constructed EAE model with age and sex matched C57BL/6 and accessed the expression of costimulatory molecules PD-L1 on the EAE .Our study may provide the rationale for developing a strategy for PD- L1 as a therapy to limit disease in EAE and multiple sclerosis.Methods:In the first part of the study, thirty female C57BL/6J mice were randomly divided into two groups: the experimental group (20) and the control group(10). the emulsionized antigen adjuvant was obtained by mixation of myelin oligodendrocyte glycoprotein(MOG35-55) and complete Freund's adjuvant(CFA) and then immunized the mice of the experimental group.Bordetella pertussis toxin(PT) was injected by tail vein on day 0 and after 24 hours while control group with PBS treatment. The clinical manifestation of each group was rated and analyzed. The spinal tissue of experiment group with apparente clinical manifestation and control group were sliced and HE,Luxol Fast-Blue stained in order to identificate the animal model successful or not.In the sencond part of the study we detect the expression of costimulatory molecules PD-L1 on the spiral by immunohistochemistry.We also accessed the expression of costimulatory molecules PD-L1 on the splenocytes by Flow cytometry and Western-Blot.Results:Most of the mice in experiment group were appeared clinical manifestation, such as action sluggish and tail paralysis, were appeared at the 10 days after antigen injected, and then gradually deteriorated .Some even were incontinent and dead.The clinical manifestation was the most serious at the 12-14 days, and then becomed improved, but they could not complete remissson.There was no above clinical manifestations in the control group.Inflammatory cells infiltrate around the blood vessel of the spinal cord tissue of experiment group mice were observed by light microscope. Extensive demyelination were detected in the white matter of the spinal cord, while there was no such change in the control group. We had abserved the mice for 30 days.The level of PD-L1 were increased both on the spiral by immunohistochemistry and on the splenocytes by Flow cytometry and Western-Blot in experimental group.Conclusions:The animal model of EAE was successfully constructed whose clinical symptoms and pathological changes were consistent with recrudescent and non- relieved EAE and the model was stable and reliable.Expression of costimulatory molecules PD-L1 was significantly increased both on the splenocytes and on the spinal cord of experimental group.