Leukocyte rolling and adhesion in inflamed yolk sac vessels during fetal development. (A) Rolling flux (number of rolling EGFP⁺ or AO⁺ cells per minute, mean ± standard error of the mean), (B) rolling flux fraction (rolling EGFP⁺ or AO⁺ cells to all EGFP⁺ or AO⁺ cells, respectively, passing the vessel per minute), and (C) adhesion (cells per square millimeter; mean ± standard error of the mean) of EGFP⁺ or AO⁺ blood cells in murine yolk sac vessels (n > 3 mice per group and n > 3 vessels per mouse). In addition, induction of EGFP⁺ (D) cell adhesion in yolk sac vessels and (E) extravasation into perivascular tissue are shown following local stimulation (superfusion) with the formyl peptide fMLP (n > 3 mice per group). Significant differences (P < .05) vs E18 (A-C) are indicated by the asterisk. anti-P, P-selectin blocking antibody.