MMP9 and multiple sclerosis: The infiltrating neutrophils have been shown to produce MMP-9 and IL-1β, which are involved in BBB dysfunction [26,27,28] and contribute to pathogenesis in animal models of neurological disease, such as the experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis [29,30], intracerebral hemorrhage [31] and ischemic stroke [32].