For instance, we have recently evidenced that CD28-mediated upregulation of pro-inflammatory cytokines (i.e., IL-8, IL-6, IL-21, and IL-17A) was higher in human primary T lymphocytes from relapsing-remitting multiple sclerosis patients (RRMS) compared with HD (17). Here, IL21 is linked to relapsing-remitting multiple sclerosis.