Electron micrographs of IL-1β–activated venules from PECAM-1–deficient and wild-type animals.

Following in vivo quantification of leukocyte responses 4 hours after intrascrotal administration of IL-1β, cremaster muscles were removed and prepared for transmission electron microscopy. Representative electron micrographs of cremasteric venules from wild-type (A) and PECAM-1–deficient (B) mice are shown. E indicates endothelium; N, neutrophil; P, pericyte and associated perivascular basement membrane. Bar represents 10 microns.