title: Sequential binding of CD11a/CD18 and CD11b/CD18 defines neutrophil capture and stable adhesion to intercellular adhesion molecule-1.
abstract: The relative contributions of CD11a/CD18 and CD11b/CD18 to the dynamics and strength of neutrophil adhesion to intercellular adhesion molecule (ICAM)-1-transfected cells were examined over the time course of chemotactic stimulation. Suspensions of neutrophils and transfectants were sheared in a cone-plate viscometer, and formation of heterotypic aggregates was measured by 2-color flow cytometry. The 2-body collision theory was used to compute adhesion efficiency, defined as the proportion of collisions between neutrophils and target cells that resulted in capture. ICAM-1 surface density and shear rate both regulated adhesion efficiency. Target cells expressing approximately 1000 ICAM-1 sites/microm(2) (I(low)) were captured with an efficiency of 0.15 at 100 s(-1), which decreased to zero at 300 s(-1). At 8-fold higher ICAM-1 expression (I(high)) corresponding to levels measured on interleukin-1-stimulated endothelium, efficiency was 0.3 at 100 s(-1) and remained above background to 900 s(-1). Shear alone was sufficient for CD11a/CD18-mediated adhesion to ICAM-1, and stimulation with formyl-methionyl-leucyl-phenylalanine boosted capture efficiency through CD11a/CD18 by 4-fold. In comparison, CD11b/CD18 supported one third of this efficiency, but was necessary for aggregate stability over several minutes of shear and at shear stresses exceeding 5 dyne/cm(2). Hydrodynamics influenced capture efficiency predominantly through the collisional contact duration, predicted to be approximately 9 milliseconds for successful capture of I(low) and 4 milliseconds for I(high). The implication is that an increase in ICAM-1 from resting levels to those on inflamed endothelium effectively increases the permissible shear in which capture through beta(2)-integrins may occur. Neutrophil adhesion to ICAM-1 appears to be a cooperative and sequential process of CD11a-dependent capture followed by CD11b-mediated stabilization.
authors.affiliation: Speros Martel Section of Leukocyte Biology, Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA.
authors.forename: E R
authors.initials: ER
authors.lastname: Hentzen
authors.forename: S
authors.initials: S
authors.lastname: Neelamegham
authors.forename: G S
authors.initials: GS
authors.lastname: Kansas
authors.forename: J A
authors.initials: JA
authors.lastname: Benanti
authors.forename: L V
authors.initials: LV
authors.lastname: McIntire
authors.forename: C W
authors.initials: CW
authors.lastname: Smith
authors.forename: S I
authors.initials: SI
authors.lastname: Simon
mesh_terms: D002448:Cell Adhesion; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002630:Chemotactic Factors / Q000494:pharmacology; D005434:Flow Cytometry; D018056:Hemorheology; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism*; D007700:Kinetics; D016169:Lymphocyte Function-Associated Antigen-1 / Q000378:metabolism*; D016177:Macrophage-1 Antigen / Q000378:metabolism*; D008956:Models, Chemical; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000378:metabolism*; D011485:Protein Binding; D013314:Stress, Mechanical; D014657:Vasculitis / Q000378:metabolism
chemical_list: D002630:Chemotactic Factors; D016169:Lymphocyte Function-Associated Antigen-1; D016177:Macrophage-1 Antigen; D018799:Intercellular Adhesion Molecule-1; D009240:N-Formylmethionine Leucyl-Phenylalanine