Cytotoxic activity of CD4 T Cells during the early stage of autoimmune neuroinflammation

Pathogenic CD4+ T cells are capable of initiating neuroinflammation in experimental autoimmune encephalomyelitis (EAE). However, the precise effector mechanism of these autoaggressive CD4+ T cells is not entirely elucidated. Here, we demonstrated that pathogenic CD4+ T cells, upon autoantigen stimulation, developed a cytotoxic phenotype at the onset of EAE. The cytotoxic activity of pathogenic CD4+ T cells was sufficient to explain the initial myelin lesion. Consistently, CD4+ T cells of peripheral blood (PBMCs) and cerebrospinal fluid (CSF) from relapse-remitting multiple sclerosis (RRMS) patients present an enhancement of the cytotoxic profile in comparison with healthy control (HC). Moreover, cytotoxic CD4+ T cells (CD4-CTLs) are restrained in the PBMCs of Natalizumab-treated RRMS patients. Mechanistically, autoaggressive CD4-CTLs matched the majority of the molecular pathways of effector CD8+ T cells. Altogether, our findings point to potential new targets for monitoring MS diagnosis, treatment, and the development of novel therapeutic avenues.