The junctional adhesion molecule JAM-C regulates polarized transendothelial migration of neutrophils in vivo

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Abstract
Neutrophils migrate into tissues as innate immune responders. Nourshargh and colleagues demonstrate that neutrophils can migrate in the reverse direction in vivo under inflammatory conditions and may contribute to the dissemination of systemic inflammation. The migration of neutrophils into inflamed tissues is a fundamental component of innate immunity. A decisive step in this process is the polarized migration of blood neutrophils through endothelial cells (ECs) lining the venular lumen (transendothelial migration (TEM)) in a luminal-to-abluminal direction. By real-time confocal imaging, we found that neutrophils had disrupted polarized TEM ('hesitant' and 'reverse') in vivo. We noted these events in inflammation after ischemia-reperfusion injury, characterized by lower expression of junctional adhesion molecule C (JAM-C) at EC junctions, and they were enhanced by blockade or genetic deletion of JAM-C in ECs. Our results identify JAM-C as a key regulator of polarized neutrophil TEM in vivo and suggest that reverse TEM of neutrophils can contribute to the dissemination of systemic inflammation.