Platelet-endothelial cell adhesion molecule-1 (PECAM-1)–deficient mice demonstrate a transient and cytokine-specific role for PECAM-1 in leukocyte migration through the perivascular basement membrane

Studies with neutralizing antibodies have indicated roles for platelet-endothelial cell adhesion molecule-1 (PECAM-1) in leukocyte migration through the endothelium and the perivascular basement membrane. Because some of these findings have been contentious, this study aimed to explore the role of PECAM-1 in leukocyte migration by analyzing leukocyte responses in interleukin 1β (IL-1β)– and tumor necrosis factor-α (TNFα)–activated cremasteric venulesof PECAM-1–deficient mice using intravital and electron microscopy. Although no differences in levels of leukocyte rolling flux or firm adhesion were observed, a delay in leukocyte transmigration in response to IL-1β, but not TNFα, was detected in PECAM-1–deficient mice. Electron microscopy indicated that this delay occurred at the level of perivascular basement membrane. To address the cytokine specificity of PECAM-1 dependence, in vitro experiments demonstrated that TNFα, but not IL-1β, could induce rapid adhesion of murine neutrophils to protein-coated surfaces, suggesting that TNFα elicited leukocyte transmigration in wild-type mice via direct stimulation of leukocytes. In summary, the results suggest a regulatory role for PECAM-1 in leukocyte migration through the perivascular basement membrane, a role that appears to be cytokine-specific and associated with the ability of the cytokine to stimulate rapid neutrophil adhesion.