Abstract
The aim of the present study was to investigate the possible role of cytotoxic T lymphocytes (CTL) and mononuclear macrophages in the pathogenic processes of experimental animals. To construct a chronic experimental allergic encephalomyelitis (EAE) model, an artificially synthesized myelin oligodendrocyte glycoprotein (MOG)35‑55 peptide was used to induce C57BL/6 mice. Subsequently, the experimental animals were investigated at the level of their nervous function, and histopathological, immunohistochemical and fluorescence immunohistochemical experiments were performed at different time points following immunization. The expression of immune molecules and cytokines associated with the activation of the mononuclear macrophages and CTL during the different stages was assessed by western blotting and reverse transcription‑quantitative polymerase chain reaction. As a result, the MOG35‑55 peptide was identified as being successful at inducing C57BL/6 mice for the development of the EAE model. A modest level of mononuclear macrophage and lymphocyte infiltration was observed in the central nervous system (CNS), although no infiltration of neutrophils was observed. A sporadic flaky deletion of the myelin sheath was also identified. The activation and proliferation of mononuclear macrophages, including microglia cells, was clearly demonstrated. Furthermore, the expression levels of major histocompatibility complex class I and II molecules and interleukin‑12 in the brain, which is associated with the activation and proliferation of mononuclear macrophages, increased over the duration of the experiment compared with less pronounced changes in the expression levels of interferon (IFN)‑γ, Fas and perforin in the CNS, which are associated with the function of CTL. The secretion of IFN‑γ in the spleen increased during the morbidity peak, however, any noticeable activation and proliferation of CD8+ T cells was absent. These results demonstrated that the induced immune response mediated by mononuclear macrophages made a more important contribution compared with CTL towards the pathological process of myelin sheath injury. Mononuclear macrophages are therefore, identified as being one of the most significant effector cell types to directly injure the myelin sheath in the CNS.