CXCR4 and Stroke: Thirty-three acute ischemic stroke patients and 15 non-stroke control subjects had their venous blood collected repeatedly in order to assess the levels of the CD45–CD34 + CD271+, the CD45–CD34 + CXCR4+, the CD45–CD34 + CXCR7+, and the CD45–CD34 + CD133+ stem/progenitor cells by means of flow cytometry.