In addition to CD8+ T cells, CD4+ T cells are also found in MS lesions and have been shown to produce cytokines such as IL-17 and IL-22 which possibly bind to BBB endothelial cells expressing IL-17 and IL-22 receptors, thereby gaining access to the CNS parenchyma (Kebir et al., 2007). Here, IL17A is linked to myeloid sarcoma.