CD4 and myeloid sarcoma: Finally, cerebral hypoperfusion in MS patients might be aggravated by ET-1 [85,184,185], together with alterations in the renin-angiotensin-aldosterone-system detected in MS patients such as decreased CSF angiotensin II levels [186], increased serum angiotensinogen converting enzyme [187] and up-regulation of angiotensin II receptor type I on myelin-autoreactive CD4+ T cells and monocytes of MS brain lesions [188].