CCL2 and myeloid sarcoma: Regarding differences in BBB permeability in relapsing MS, there are inflammatory infiltrates with focal breakdown of the blood-brain barrier due to tight junction (TJ) pathology, lymphocyte infiltration, and upregulation of proinflammatory cytokines and chemokines such as IL-1β, IL-17, IL-22, IFN-γ, and CCL2.