| Objective: Multiple sclerosis (MS) is an autoimmune disease of the central nervous system (CNS), its morbidity mounting year by year all over the world. As a main neurological disease leading to impairment of young and middle-aged people, it has become a severe harm to our labour recourse and human health. However, ideal therapy has not yet been established at present. Experimental autoimmune encephalomyelitis (EAE) is a T cell-medicated demyelinating disease of the CNS and a putative model of the human demyelinating disease MS. They share many similarities with each other, such as immunized antigens, clinical signs, histological examination, pathologic mechanisms and so on. Oral tolerance by feeding autoantigen to animal model is now a study focus to prevent and treat EAE and MS. Although its mechanism has not been very clear, the therapy has received more and more attentions from all sides. Based on the EAE model of rats, immune tolerance is induced by the extracted myelin as auto-oral antigen. In various stages of the course, the mRNA expression of cytokines such as tumour necrosis factor- a(TNF- a ) and transforming growth factor- P (TGF- P ) are analysed at molecular level in the oral group and the control group respectively. Furthermore, the status of apoptotic cell are simultaneously detected in the peripheral lymphoid organs and the CNS, and the possible mechanism of immune tolerance is discussed, which provided evidences for the prevention and treat of EAE and MS.Methods: The present study is made up of three sections. Section one is about the extraction and identification of the myelin, which was obtained from white matter of bovine spinal cord by discontinuous grandient centrifugation, then its main compositions and relative molecule weight being identificated by SDS-polyacrylamide gel electrophoresis. Additionally, its immunologic activity was observed by inducing EAE in guinea pigs. The result shows, the extracted myelin is mainly composed of high molecular weight myelin basic protein (MBP) and has high encephaliotogenic activity, and can be used to induce EAE successfully. Section two is about the induction and clinical assessment of EAE. The rat EAE was successfully induced by subcutaneous injection into the four footpats with guinea pig spinal cord homogenate (GPSCH) emulsified in complete Freund's adjuvant (CFA), accompanied by intracutaneous injection into one foot with pertussis toxin. Section three consists of the study of preventing EAE by oral myelin and the possible mechanism of oral tolerance. The rats were fedwith myelin on days 7, 5, 2 before immunization, the day immunized and days 2, 5, 7 after immunization, with a dose of 5 mg meylin per rat per day, and total dose 35 mg per rat. The day of immunization is noted as day 0. Immunized rats were observed daily for clinical signs of EAE and sacrified under ether anesthesia on days 9, 13 and 23 after immunization. Their lymph nodes and spleens were removed and total RNA were extracted from the mononuclear cells (MNCs) of fresh lymph nodes to detect the mRNA expression of cytokines (TNF- a and TGF- P ) by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR). Meanwhile, to assess apoptosis in the peripheral lymphoid organs, we extracted MNCs from the lymph nodes and spleens respectively and performed flow cytometric analysis (FCM) of their DNA stained with propidium iodide. Besides, the lymph nodes, spleens, brains and lumbar spinal cords were removed and embeded with paraffin for HE staining and TUNEL detection. The results were compared with that of the control group, and processed by statistical analysis as follows:Results: 1. The earliest onset of rat in the control group takes on in day 9 after immunization, and the average onset time was day 10.1+1.6 after immunization, while that of the oral group was later than the former, and its average onset time was day 11.8+2.4 after immunization. Compared with the control group, the morbidity of the oral group wasdecreased from 90% to 70% (P>0.05...
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