TNF and myeloid sarcoma: Soluble factors secreted by microglia that participate in negative effects in the pathogenesis of MS include IFN-γ, tumor necrosis factor-alpha (TNF-α), reactive oxygen species, interleukin 1β (IL-1β), IL-6, IL-18, IL-12 and IL-23 and also chemokines such as CCL2, CCL3, CCL4, CCL5, CCL7, CCL12 and CCL22 [5,17,56,57] (Figure 2).