DCs are antigen presenting cells (APCs) that participate in the initiation and development of multiple sclerosis.68 In the periphery, DCs activate naïve CD4+ T cells into CD4+ Th1 and Th17 cells, that in turn cross the BBB and are reactivated in the perivascular and subarachnoid CNS spaces by resident APCs allowing them to infiltrate the CNS parenchyma.69,70. This evidence concerns the gene CD4 and multiple sclerosis.