Leukocyte rolling velocity histograms. Leukocyte rolling velocities in (A) control PBS and (B) IVIG-treated sickle cell mice. Arrowheads indicate the means. The mean is significantly higher in the IVIG group than in PBS controls. *P < .05. Cumulative frequency histograms of (C) rolling velocities and (D) leukocyte transit times. Median values are indicated by vertical lines.