The pathogenesis of multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE), is primarily mediated by T cells. However, recent studies have only focused on CD4 + T-helper cells that secrete interleukin-17 (IL-17), also known as Th17 cells. This study aims to determine the similarities and differences between Th17 cells and CD8+ T-cytotoxic cells that secrete IL-17 (Tc17) in the context of MS/EAE.
Female C57BL/6 mice (n = 20) were immunized with myelin oligodendrocyte glycoprotein peptides 35–55 (MOG35 − 55), pertussis toxin, and Complete Freund’s adjuvant to establish the EAE animal model. T-cells were isolated from the spleen (12–14 days post-immunization) and purified into CD4+ and CD8+ using flow cytometry. These cells were differentiated into Tc17 and Th17 using MOG35-55 and IL-23. Secretion levels of interferon-γ (IFN-γ) and IL-17 were measured via enzyme-linked immunosorbent assay (ELISA) using cultured CD4+ and CD8+ T-cells supernatant. Pathogenicity of Tc17 and Th17 cells was tested through adoptive transfer (tEAE), with the clinical course assessed using an EAE score (0–5). Hematoxylin and eosin and Luxol fast blue staining were used to examine the spinal cord.
Purified CD8+CD3+ and CD4+CD3+ cells were differentiated into Tc17 and Th17 cells, and then stimulated with MOG35 − 55 peptide for proliferation assays. The results showed that Tc17 cells exhibited a weaker response to MOG35 − 55 compared to Th17 cells. However, this response was not dependent on Th17 cells. Tc17 cells secreted lower levels of IFN-γ and IL-17. In the tEAE mouse model, similar EAE scores and slight inflammation and demyelination were observed in Tc17 cell-induced tEAE mice compared to Th17 cell-induced tEAE mice.
Although Tc17 cells were pathogenic in EAE, their degree of pathogenicity was lower than that of Th17 cells. Tc17 cells secreted similar levels of IL-17 to Th17 cells after antigen stimulation, but their IFN-γ secretion was significantly lower.