Neutrophils migrate through enlarged pericyte gaps. (A) The graph shows the frequency (percentage) of different sized gaps between adjacent pericytes in cremasteric postcapillary venules (unstimulated and TNF-stimulated) as detected by ex vivo immunofluorescence labeling and confocal microscopy. Gap sizes in the depicted range (1–52 µm²) represent ∼97% of all detected gaps (at least 4 venules per animal analyzed in 5 mice). The boxed region indicates the range of gaps used by ∼70% of observed transmigration events as analyzed by 4D confocal IVM (significantly different from the frequency of transmigration events detected in the nonboxed range; ***, P < 0.001). (B) Quantification of MFI per unit area of ICAM-1 (left) and KC (right) on pericyte cell body and at pericyte gap borders (a 2-µm wide region surrounding the gaps) after TNF-stimulation (3 h). Results are expressed as mean of at least n = 11 (A) and n = 5 (B) mice per group, respectively (with 3–4 vessels/cremaster, 2 cremasters/animal).