Localization of trapped neutrophils during diapedesis in cremaster venules by electron microscopy. (A-B) Proportion of neutrophils trapped between endothelial cells (A) and between endothelial cells and the basement membrane (B) in IL-1β-treated cremaster muscles. Analysis was done by transmission electron microscopy. Animals were treated with preimmune control antibodies (co-IgG), affinity-purified anti-CD99 antibodies (anti-CD99), a mixture of 2 mAb against mouse PECAM-1 (anti–PECAM-1), or control IgG F(ab′)2 or anti-CD99 F(ab′)2 (as indicated). Graphs represent the number of trapped neutrophils given as percentage of leukocytes that had passed the endothelial cell contacts. For each determination, 30 to 52 randomly selected vessel segments were analyzed. ***P < .001. *P < .05. Statistical analysis was done by ANOVA evaluating all available data. (C) Electron micrographs of vessel segments of IL-1β inflamed cremaster muscle of mice treated with control antibody from the preimmune serum (co-IgG) and affinity-purified anti-CD99 antibodies (anti-CD99). Positions of neutrophils (red) and endothelium (blue) are given in the cartoons at the bottom. Bar represents 5 μm.
