Natalizumab induced mobilization. (A) CD34⁺ cells/μL in the peripheral blood of 20 MS patients receiving natalizumab 300 mg intravenously each month. Natalizumab patients were examined 28 days following the last infusion. For comparison, 5 healthy volunteers and 5 untreated MS patients were analyzed too. (Diamonds indicate the individual amount of CD34⁺ cells per patient; bars indicate the median number of CD34⁺ cells/μL in each group, brackets indicate statistical significance between groups using Mann-Whitney test.) (B) Sequential analysis of natalizumab-induced mobilization of CD34⁺ cells into peripheral blood of 4 MS patients before and 1 hour, 24 hours, 48 hours, 72 hours, and 1 month following infusion. MS patients received a single intravenous infusion of 300 mg natalizumab; peripheral venous blood was taken at time intervals after drug administration; FACS analyses were performed to determine the concentration of CD34⁺ cells. Brackets indicate statistical significance expressed as P value compared with baseline (time = before) using 2-sided paired t test.