MBP and myeloid sarcoma: Regarding the relevance of CXCL12 in vivo several groups have already demonstrated that in the MS brain CXCL12 is expressed by reactive astrocytes particularly near the lesion edge [32] and that the proinflammatory cytokine interleukin-1β and myelin debris in the form of MBP can induce astrocytic CXCL12 [33].