Regulation of cell adhesion molecule expression and function associated with neutrophil apoptosis

We have investigated the adhesive capacity of neutrophils after spontaneous apoptosis, which occurs during in vitro culture. Apoptotic neutrophils show reduced adhesion to E selectin and the CD18 integrin ligand fibrinogen. Neutrophil apoptosis is associated with changes in the levels of surface expression of key receptors that mediate neutrophil adhesion events. Notably, apoptotic neutrophils show reduced expression of L-selectin/selectin ligand. In contrast, CD11b/CD18 and CD11c/CD18 integrins are expressed at increased levels. The reduced capacity for adhesion of apoptotic neutrophils may be achieved by very different mechanisms. Regulation of the levels of surface expression of receptors/ligand may control selectin-mediated adhesion, possibly as a result of protease/sialidase activity. In contrast, modulation of integrin-mediated adhesion may involve functional uncoupling of receptors present on the surface of the apoptotic cell without alteration in levels of surface expression. The altered adhesive potential of the apoptotic neutrophil may serve to limit release of its histotoxic contents and reduce inappropriate tissue injury.