CX3CR1 drives cytotoxic CD4+CD28− T cells into the brain of multiple sclerosis patients

► CD4+CD28− T cells are characteristic of immunosenescence. ► CD4+CD28− T cells are cytotoxic after polyclonal or antigen-specific stimulation. ► CD4+CD28− T cells are effector-memory T cells which express CX3CR1. ► Fractalkine (CX3CL1) is upregulated in the CSF and brain of MS patients. ► CD4+CD28− T cells infiltrate the inflamed brain lesions of MS patients.