refers to damage to tissue caused when blood supply returns to the tissue after a period of ischemia. The absence of oxygen and nutrients from blood creates a condition in which the restoration of circulation results in inflammation and oxidative damage through the induction of oxidative stress rather than restoration of normal function.

The damage of reperfusion injury is due in part to the inflammatory response of damaged tissues. White blood cells carried to the area by the newly returning blood release a host of inflammatory factors such as interleukins as well as free radicals in response to tissue damage^[1]. The restored blood flow reintroduces oxygen within cells that damages cellular proteins, DNA, and the plasma membrane.

Receptors that are expressed on the surface of endothelial cells , leukocytes , or platelets and endothelial cells [2] C. Berlin, E.L. Berg, M.J. Briskin, D.P. Andrew, P.J. Kilshaw and B. Holzmann et al., Alpha 4 beta 7 integrin mediates lymphocyte binding to the mucosal vascular addressin MAdCAM-1, Cell 74 (1993), pp. 185–195. Abstract | View Record in Scopus | Cited By in Scopus (. Selectins are involved in mediating the rolling of leukocytes on the surface of the endothelium through interactions with their respective ligands.

E- and P-selectins

E-selectin is expressed by unstimulated endothelial cells under physiological conditions, mediates neutrophil adhesion and is up-regulated by pro-inflammatory cytokines in an NF-κB-dependent manner .

P-selectin is expressed at low levels by resting endothelial cells and platelets, with rapid and short-lived translocation to the plasma membrane after activation of cells with LPS, TNF-α and thrombin

The P-selectin glycoprotein ligand , which is able to bind to all three selectins , is a sialoprotein with a high-affinity binding site, which is expressed on the surface of leukocytes

L-selectin is present on all leukocytes, but interestingly the only pro-inflammatory cytokine that has been demonstrated to upregulate its expression is TNFα

the main ligand for L-selectin are two glycoproteins expressed on endothelial cells: GlyCAM-1 and CD34

Integrins are heterodimeric proteins of α and β subunits. Leukocytes can express 13 different integrins but 5 of these glycoproteins are the major modulators of leukocyte–endothelial cell adhesion:

5 major modulators belong to β₁, β₂, and β₇ subfamilies (α₁β₂, α₂β₂, α₃β₂, α₄β₁, α₄β₇)