Figure 1.

Pathogenic T helper (Th) cell subsets in multiple sclerosis (MS). Self-reactive Th1, Th22 cell, and Th1-like Th17 subsets activated in peripheral lymph nodes cross the blood–brain barrier (BBB) and migrate into the central nervous system (CNS). In the CNS, T cells are reactivated and, by producing their lineage-defining cytokines, regulate the functions of CNS-resident cells (microglia, astrocytes, oligodendrocytes) by enhancing inflammatory cytokine production, antigen-presenting cell (APC) functions, and apoptosis, thus contributing to axonal damage and demyelination.