The role of leukocyte chemotaxis in inflammation

The movement of leukocytes from blood into the tissues in response to inflammatory stimuli was observed and described as early as 1891 by Metchnikoff1 and 1888 by Leber2; however, only within the past few decades has some light been shed on the cellular and molecular mechanisms involved in the process of leukocyte emigration. During inflammation, blood leukocytes:(1) marginate and adhere to the endothelial cells of the postcapillary venules,(2) migrate across the endothelial cell layer and basal membrane, and (3) move in the tissues towards the source of inflammation where they fulfil their function in host defence. Whereas altered parameters of circulation and the expression of recently identified adhesion molecules by the leukocytes and endothelial cells are responsible for margination and adhesion, the chemotaxis of leukocytes (their capacity of directed movement along a concentration gradient of molecules referred to as chemotaxins or chemoattractants) is considered essential for leukocyte emigration and movement in extravascular tissues.