MPO and myeloid sarcoma: In the blood of MS patients, increased concentrations of neutrophil-activating chemokines, granulocyte recruiting chemokines, and neutrophil-derived enzymes are detected (e.g., CXCL1, CXCL8, CXCL5, NE, MPO) and these molecules are associated with the formation of new inflammatory lesions and correlated with measures of MS lesion burden and clinical disability (24, 25).