Margination

Margination is the process in which free-flowing leukocytes exit the central blood stream, and initiate leukocyte and endothelial cell interactions by close mechanical contact. The underlying mechanisms of margination involve the interaction of leukocytes with erythrocytes flowing in the same microvessel, whereby deformed erythrocytes push leukocytes to a marginating position due to their smaller cross section and higher flow velocity.

Erythrocyte aggregation also promotes margination in large microvessles because cell aggregates occupy the center of the venule. The variablity of aggregation between mammaliam species may suggest that this particular mechanism is not critical in the inflammatory process. Rheological margination is not critical for the initiation of leukocyte rolling or inflammation because leukocytes leave capillaries whose diameter is smaller than their own, and leukocyte contact with the endothelium is ensured.

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