Neutrophils live for just a few days after entering the circulation. But what dramatic days! Incited by an infection, the cells mature from the bone marrow and flood into blood vessels, hot for combat, their faces granulated, their nuclei dilated—a fleet of teenage soldiers deployed to battle. They have evolved special mechanisms to move quickly through tissues, squirming their way through blood vessels like contortionists. It is as if they are maniacally driven to reach sites of infection and inflammation—in part, because they so keenly perceive the gradient of cytokines and chemokines
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