The process in which leukocytes are able to move across capillaries within tissues. Initiated by complement factor C5a and proinflammatory and chemotactic cytokines released by nearby macrophages and tissues. These components promote the expression of cellular adhesion molecules, which bind to leukocytes and lead to transendothelial migration. Leukocytes then exit the bloodstream and reach the infected areas to begin their pathogen attack. Some leukocytes respond faster than others, with neutrophils responding within hours and monocytes taking up to days.

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