Chemo-attractant N-acetyl proline-glycine-proline induces CD11b/CD18-dependent neutrophil adhesion.

BACKGROUND: Chronic inflammation in lung diseases contributes to lung tissue destruction leading to the formation of chemotactic collagen fragments such as N-acetylated proline-glycine-proline (N-ac-PGP). In the current study, we investigate whether N-ac-PGP influences beta(2)-integrin activation and function in neutrophilic firm adhesion to endothelium. METHODS: Human polymorphonuclear leukocytes (PMNs) were isolated from fresh human blood. Subsequently, a transmigration assay was performed to evaluate the active migration of PMNs towards N-ac-PGP. Furthermore, the effect of the tripeptide on beta(2)-integrin activation was assessed by performing the adhesion assay using fibrinogen as a ligand. To determine whether this effect was due to conformational change of beta(2)-integrins, antibodies against CD11b and CD18 were used in the adhesion assay and the expression pattern of CD11b was determined. RESULTS: Human neutrophils transmigrated through an endothelial cell layer in response to basolateral N-ac-PGP. N-ac-PGP induced also a neutrophil adherence to fibrinogen. Using functional blocking antibodies against CD11b and CD18, it was demonstrated that CD11b/CD18 (Mac-1) was responsible for the N-ac-PGP-induced firm adhesion of neutrophils to fibrinogen. Pertussis toxin decreased the Mac-1 activation indicating the involvement of G-proteins. N-ac-PGP most likely activated Mac-1 by initiating a conformational change, since the expression pattern of Mac-1 on the cell surface did not change significantly. CONCLUSIONS: Chemo-attractant N-acetyl proline-glycine-proline induces CD11b/CD18-dependent neutrophil adhesion. GENERAL SIGNIFICANCE: This is the first study to describe that the chemo-attractant N-ac-PGP also activates Mac-1 on the surface of neutrophils, which can additionally contribute to neutrophilic transmigration into the lung tissue during lung inflammation.