Figure 3.

Leukocyte migration. Leukocytes leave the blood and migrate to sites of infection. Sialyl-Lewis^X on leukocytes binds to selectins P and E on endothelial cells. This binding becomes stronger when CXCL-8 binds to its specific receptor on neutrophils, triggering the production of integrin LFA-1 and CX3 (mac-1). Inflammatory cytokines, such as TNF-α, are also necessary to induce expression of the adhesion molecules ICAM-1 and ICAM-2. The interaction between endothelial cells and ICAM-1 allows the passage of neutrophils along a gradient of chemoattractants substances.