Studies On Dendritic Cells In The Onset And Oral Tolerance Of Experimental Allergic Encephalomyelitis

EAE is a T-cell-mediated demyelinating disease of CNS and a typical model of MS. Oral tolerance by feeding autoantigens is an effective method to prevent EAE and to treat MS, which mechanism has not been made very clear. Studies of the initiators of immune responses, like DCs, are lacking. The present study is made up of two sections. Section one is the induction of EAE and oral tolerance. The EAE rat were successfully induced by injecting intracutaneously an emulsion of GPSCH and CFA to rats with the dose of 0.4ml per rat. In addition, each rat received an intrapertoneal injection of 2.5×109 pertussis. Oral tolerance was induced by oral administration of myelin which was extracted by discontinuous gradient centrifugation from fresh bovine spinal cord. The rats were fed with 5mg myelin on day 7,5,2 before inoculation, the day of inculation and the day 2,5,7 post inculation. Section two is the study of DCs' role in EAE and oral tolerance. On the days of 4,7,9,15,23 p.i., the rats were perfused through aorta with 2% PBS-formaldehyde before ilium and armpit lymph nodes, then, brains and spinal cords were removed for cryostat sections cutting. These sections were used for HE staining, immunofluorescence staining. Other ilium and armpit lymph nodes were removed before perfused for flow cytometric analysis. The results were compared with those from control group as following:1. The rats of oral group had an attack beginning on 12d p.i., which of the EAE group is on 10d p.i.. On 15d p.i., the symptoms reached the peak. At this time, the morbidity rate of oral group was 22.2%(n=18), compared with 77.8%(n=18) of the EAE group. There was significant difference in the severity of clinical symptoms between two groups (oral group, 0.56±1.13,n=18; EAE group, 1.44± 1.13,n=18;P<0.05). The foci in the section of the rat brains and spinal cords in oral group were less and less dense immunofluorescence than those of the EAE group.2. The numbers of CD11c, CD86 positive cells in ilium and armpit lymph nodes were increasing on 4d p.i., and decreasing on 15d p.i, CD11c+, CD86+DCs appeared in the spinal cords and brains before EAE onset. But there was little significant difference between oral group and EAE group. On 15d p.i. and 23d p.i., the numbers of CD11c+, CD86+cells are accordant to the symptoms of the inflammation of brains and spinal cords.3. Flow cytometric analysis indicated that there was little significant difference between oral and EAE group, but there was significant difference between oral or EAE and control group (P<0.05). There were significant differences beteewn control group and clinical different symptom subgroups.Conclusion1. The MS animal model EAE was induced in Wistar rats byimmunization with GPSCH+CFA+pertussis, which is economicaland feasible.2. The morbidity rate and the severity of EAE rats were decreased by feeding myelin.3. DCs, located in peripheral lymph nodes and CNS, play an important role in EAE onset, development and recovery, especially in EAE onset.4. Many mechanisms, such as clonal deletion, active suppression, and so on, are involved in the oral tolerance. DCs, as an initiator of immune response, may play a secondary role in the mechanism of oral tolerance.