The Experts below are selected from a list of 8343 Experts worldwide ranked by ideXlab platform
Ulrich H. Von Andrian - One of the best experts on this subject based on the ideXlab platform.
-
C1q Governs Deposition of Circulating Immune Complexes and Leukocyte Fcγ Receptors Mediate Subsequent Neutrophil Recruitment
The Journal of experimental medicine, 2004Co-Authors: Tracy Stokol, Ulrich H. Von Andrian, Peter E. O'donnell, Ling Xiao, Sara Knight, George Stavrakis, Marina Botto, Tanya N. MayadasAbstract:Inflammation induced by circulating immunoglobulin G–immune complexes (ICs) characterizes many immune-mediated diseases. In this work, the molecular requirements for the deposition of circulating ICs and subsequent acute leukocyte recruitment in mice were elucidated. We show that after intravenous injection, preformed soluble ICs are rapidly deposited in the postcapillary venules of the cremaster microcirculation, secondary to increased vascular permeability. This deposition is dependent on complement C1q. IC deposition is associated with leukocyte recruitment. Leukocyte Rolling, which is mediated by P-selectin in the exteriorized cremaster muscle, is not further increased in response to ICs. In contrast, leukocyte Rolling Velocity is significantly decreased and leukocyte adhesion is significantly increased in the presence of ICs. The IC-mediated slow leukocyte Rolling Velocity and subsequent adhesion and emigration are dependent on Fcγ receptors (FcγRs), particularly FcγRIII, with complement C3 and C5 having no detectable role. These studies suggest a regulatory mechanism of IC deposition and leukocyte trafficking in IC-mediated inflammation requiring C1q and FcγRs in sequential, noninteracting roles.
-
L-selectin–mediated Leukocyte Adhesion In Vivo: Microvillous Distribution Determines Tethering Efficiency, But Not Rolling Velocity
The Journal of experimental medicine, 1999Co-Authors: Jens V Stein, Guiying Cheng, Britt M Stockton, Brian P Fors, Eugene C Butcher, Ulrich H. Von AndrianAbstract:Adhesion receptors that are known to initiate contact (tethering) between blood-borne leukocytes and their endothelial counterreceptors are frequently concentrated on the microvilli of leukocytes. Other adhesion molecules are displayed either randomly or preferentially on the planar cell body. To determine whether ultrastructural distribution plays a role during tethering in vivo, we used pre-B cell transfectants expressing L- or E-selectin ectodomains linked to transmembrane/intracellular domains that mediated different surface distribution patterns. We analyzed the frequency and Velocity of transfectant Rolling in high endothelial venules of peripheral lymph nodes using an intravital microscopy model. Ectodomains on microvilli conferred a higher efficiency at initiating Rolling than random distribution which, in turn, was more efficient than preferential expression on the cell body. The role of microvillous presentation was less accentuated in venules below 20 μm in diameter than in larger venules. In the narrow venules, tethering of cells with cell body expression may have been aided by forced margination through collision with erythrocytes. L-selectin transfected cells rolled 10-fold faster than E-selectin transfectants. Interestingly, Rolling Velocity histograms of cell lines expressing equivalent copy numbers of the same ectodomain were always similar, irrespective of the topographic distribution. Our data indicate that the distribution of adhesion receptors has a dramatic impact on contact initiation between leukocytes and endothelial cells, but does not play a role once Rolling has been established.
Jens V Stein - One of the best experts on this subject based on the ideXlab platform.
-
l selectin mediated leukocyte adhesion in vivo microvillous distribution determines tethering efficiency but not Rolling Velocity
Journal of Experimental Medicine, 1999Co-Authors: Jens V Stein, Guiying Cheng, Britt M Stockton, Brian P Fors, Eugene C Butcher, Ulrich H Von AndrianAbstract:Adhesion receptors that are known to initiate contact (tethering) between blood-borne leukocytes and their endothelial counterreceptors are frequently concentrated on the microvilli of leukocytes. Other adhesion molecules are displayed either randomly or preferentially on the planar cell body. To determine whether ultrastructural distribution plays a role during tethering in vivo, we used pre-B cell transfectants expressing L- or E-selectin ectodomains linked to transmembrane/intracellular domains that mediated different surface distribution patterns. We analyzed the frequency and Velocity of transfectant Rolling in high endothelial venules of peripheral lymph nodes using an intravital microscopy model. Ectodomains on microvilli conferred a higher efficiency at initiating Rolling than random distribution which, in turn, was more efficient than preferential expression on the cell body. The role of microvillous presentation was less accentuated in venules below 20 μm in diameter than in larger venules. In the narrow venules, tethering of cells with cell body expression may have been aided by forced margination through collision with erythrocytes. L-selectin transfected cells rolled 10-fold faster than E-selectin transfectants. Interestingly, Rolling Velocity histograms of cell lines expressing equivalent copy numbers of the same ectodomain were always similar, irrespective of the topographic distribution. Our data indicate that the distribution of adhesion receptors has a dramatic impact on contact initiation between leukocytes and endothelial cells, but does not play a role once Rolling has been established.
-
L-selectin–mediated Leukocyte Adhesion In Vivo: Microvillous Distribution Determines Tethering Efficiency, But Not Rolling Velocity
The Journal of experimental medicine, 1999Co-Authors: Jens V Stein, Guiying Cheng, Britt M Stockton, Brian P Fors, Eugene C Butcher, Ulrich H. Von AndrianAbstract:Adhesion receptors that are known to initiate contact (tethering) between blood-borne leukocytes and their endothelial counterreceptors are frequently concentrated on the microvilli of leukocytes. Other adhesion molecules are displayed either randomly or preferentially on the planar cell body. To determine whether ultrastructural distribution plays a role during tethering in vivo, we used pre-B cell transfectants expressing L- or E-selectin ectodomains linked to transmembrane/intracellular domains that mediated different surface distribution patterns. We analyzed the frequency and Velocity of transfectant Rolling in high endothelial venules of peripheral lymph nodes using an intravital microscopy model. Ectodomains on microvilli conferred a higher efficiency at initiating Rolling than random distribution which, in turn, was more efficient than preferential expression on the cell body. The role of microvillous presentation was less accentuated in venules below 20 μm in diameter than in larger venules. In the narrow venules, tethering of cells with cell body expression may have been aided by forced margination through collision with erythrocytes. L-selectin transfected cells rolled 10-fold faster than E-selectin transfectants. Interestingly, Rolling Velocity histograms of cell lines expressing equivalent copy numbers of the same ectodomain were always similar, irrespective of the topographic distribution. Our data indicate that the distribution of adhesion receptors has a dramatic impact on contact initiation between leukocytes and endothelial cells, but does not play a role once Rolling has been established.
Ulrich H Von Andrian - One of the best experts on this subject based on the ideXlab platform.
-
l selectin mediated leukocyte adhesion in vivo microvillous distribution determines tethering efficiency but not Rolling Velocity
Journal of Experimental Medicine, 1999Co-Authors: Jens V Stein, Guiying Cheng, Britt M Stockton, Brian P Fors, Eugene C Butcher, Ulrich H Von AndrianAbstract:Adhesion receptors that are known to initiate contact (tethering) between blood-borne leukocytes and their endothelial counterreceptors are frequently concentrated on the microvilli of leukocytes. Other adhesion molecules are displayed either randomly or preferentially on the planar cell body. To determine whether ultrastructural distribution plays a role during tethering in vivo, we used pre-B cell transfectants expressing L- or E-selectin ectodomains linked to transmembrane/intracellular domains that mediated different surface distribution patterns. We analyzed the frequency and Velocity of transfectant Rolling in high endothelial venules of peripheral lymph nodes using an intravital microscopy model. Ectodomains on microvilli conferred a higher efficiency at initiating Rolling than random distribution which, in turn, was more efficient than preferential expression on the cell body. The role of microvillous presentation was less accentuated in venules below 20 μm in diameter than in larger venules. In the narrow venules, tethering of cells with cell body expression may have been aided by forced margination through collision with erythrocytes. L-selectin transfected cells rolled 10-fold faster than E-selectin transfectants. Interestingly, Rolling Velocity histograms of cell lines expressing equivalent copy numbers of the same ectodomain were always similar, irrespective of the topographic distribution. Our data indicate that the distribution of adhesion receptors has a dramatic impact on contact initiation between leukocytes and endothelial cells, but does not play a role once Rolling has been established.
Daniel A. Hammer - One of the best experts on this subject based on the ideXlab platform.
-
A semianalytic model of leukocyte Rolling.
Biophysical journal, 2004Co-Authors: Ellen F. Krasik, Daniel A. HammerAbstract:Rolling allows leukocytes to maintain adhesion to vascular endothelium and to molecularly coated surfaces in flow chambers. Using insights from adhesive dynamics, a computational method for simulating leukocyte Rolling and firm adhesion, we have developed a semianalytic model for the steady-state Rolling of a leukocyte. After formation in a force-free region of the contact zone, receptor-ligand bonds are transported into the trailing edge of the contact zone. Rolling Velocity results from a balance of the convective flux of bonds and the rate of dissociation at the back edge of the contact zone. We compare the model's results to that of adhesive dynamics and to experimental data on the Rolling of leukocytes, with good agreement. We calculate the dependence of Rolling Velocity on shear rate, intrinsic forward and reverse reaction rates, bond stiffness, and reactive compliance, and use the model to calculate a state diagram relating molecular parameters and the dynamic state of adhesion. A dimensionless form of the analytic model permits exploration of the parameters that control Rolling. The chemical affinity of a receptor-ligand pair does not uniquely determine Rolling Velocity. We elucidate a fundamental relationship between off-rate, ligand density, and reactive compliance at the transition between firm and Rolling adhesion. The model provides a rapid method for screening system parameters for the potential to mediate Rolling.
-
Cell separation mediated by differential Rolling adhesion.
Biotechnology and bioengineering, 2001Co-Authors: Adam W. Greenberg, Daniel A. HammerAbstract:Recently, we showed a correlation between the maturity of hematopoietic stem and progenitor cells during development and Rolling efficiency on selectins. These findings motivated us to explore a novel separation that exploits differences in selectin-mediated Rolling adhesion between populations of cells. We extend the use of a previously developed cell-free system to study the separation of populations of sialyl Lewis x (sLe(x))-coated microspheres designed to roll with different average velocities on L-selectin chimeric substrates under well-defined flow. Results show that a separation that exploits differences in average Rolling velocities between cell or microsphere populations is attainable. Excellent recovery and purity values for the slower Rolling, or more desirable, populations are obtained and can be estimated from Rolling Velocity measurements. We also assess the feasibility of a selectin-mediated separation of adult bone marrow cell populations using previously obtained Rolling Velocity and Rolling flux data for CD34+ and CD34- adult bone marrow cells on L-selectin substrates. We believe that a cell separation mediated by differential Rolling adhesion can be used to enrich populations of hematopoietic stem and progenitor cells from an adult bone marrow cell preparation and that this method possesses several major advantages over existing antibody-mediated cell-affinity chromatography technologies.
-
Hydrodynamic Collisions Suppress Fluctuations in the Rolling Velocity of Adhesive Blood Cells
Langmuir, 2001Co-Authors: Michael R. King, And Stephen D. Rodgers, Daniel A. HammerAbstract:The slow Rolling motion of white blood cells transiently adhering to the interior surface of venules under shear is simulated numerically. Molecular bond breakage events cause a noisiness in rollin...
-
Adhesive Dynamics Simulations of Sialyl-Lewisx/E-selectin-Mediated Rolling in a Cell-Free System
Biophysical journal, 2000Co-Authors: Kai-chien Chang, Daniel A. HammerAbstract:Selectin-mediated leukocyte Rolling is crucial for the proper function of the immune response. Recently, selectin-mediated Rolling was recreated in a cell-free system (Biophysical Journal 71:2902-2907 (1996)); it was shown that sialyl Lewis(x) (sLe(x))-coated microspheres roll over E-selectin-coated surfaces under hydrodynamic flow. The cell-free system removes many confounding cellular features, such as cell deformability and signaling, allowing us to focus on the role of carbohydrate/selectin physical chemistry in mediating Rolling. In this paper, we use adhesive dynamics, a computational method that allows us to simulate adhesion, to analyze the experimental data produced in the cell-free system. We simulate the effects of shear rate, ligand density, and number of receptors per particle on Rolling Velocity and compare them with experimental results obtained with the cell-free system. If we assume the population of particles is homogeneous in receptor density, we predict that particle Rolling Velocity calculated in simulations is more sensitive to shear rate than found in experiments. Also, the calculated Rolling Velocity is more sensitive to the number of receptors on the microspheres than to the ligand density on the surface, again in contrast to experiment. We argue that heterogeneity in the distribution of receptors throughout the particle population causes these discrepancies. We improve the agreement between experiment and simulation by calculating the average Rolling Velocity of a population whose receptors follow a normal distribution, suggesting heterogeneity among particles significantly affects the experimental results. Further comparison between theory and experiment yields an estimate of the reactive compliance of sLe(x)/E-selectin interactions of 0.25 A, close to that reported in the literature for E-selectin and its natural ligand (0.3 A). We also provide an estimate of the value of the intrinsic association rate (between 10(4) and 10(5) s(-1)) for the formation of sLe(x)/E-selectin bonds.
-
Cell-Free Rolling Mediated by L-Selectin and Sialyl Lewisx Reveals the Shear Threshold Effect
Biophysical journal, 2000Co-Authors: Adam W. Greenberg, D.k. Brunk, Daniel A. HammerAbstract:Abstract The selectin family of adhesion molecules mediates attachment and Rolling of neutrophils to stimulated endothelial cells. This step of the inflammatory response is a prerequisite to firm attachment and extravasation. We have reported that microspheres coated with sialyl Lewis x (sLe x ) interact specifically and roll over E-selectin and P-selectin substrates (Brunk et al., 1996; Rodgers et al., 2000). This paper extends the use of the cell-free system to the study of the interactions between L-selectin and sLe x under flow. We find that sLe x microspheres specifically interact with and roll on L-selectin substrates. Rolling Velocity increases with wall shear stress and decreases with increasing L-selectin density. Rolling velocities are fast, between 25 and 225 μ m/s, typical of L-selectin interactions. The variability of Rolling Velocity, quantified by the variance in Rolling Velocity, scales linearly with Rolling Velocity. Rolling flux varies with both wall shear stress and L-selectin site density. At a density of L-selectin of 800 sites/ μ m 2 , the Rolling flux of sLe x coated microspheres goes through a clear maximum with respect to shear stress at 0.7 dyne/cm 2 . This behavior, in which the maintenance and promotion of Rolling interactions on selectins requires shear stress above a threshold value, is known as the shear threshold effect. We found that the magnitude of the effect is greatest at an L-selectin density of 800 sites/ μ m 2 and gradually diminishes with increasing L-selectin site density. Our study is the first to reveal the shear threshold effect with a cell free system and the first to show the dependence of the shear threshold effect on L-selectin site density in a reconstituted system. Our ability to recreate the shear threshold effect in a cell-free system strongly suggests the origin of the effect is in the physical chemistry of L-selectin interaction with its ligand, and largely eliminates cellular features such as deformability or topography as its cause.
Britt M Stockton - One of the best experts on this subject based on the ideXlab platform.
-
l selectin mediated leukocyte adhesion in vivo microvillous distribution determines tethering efficiency but not Rolling Velocity
Journal of Experimental Medicine, 1999Co-Authors: Jens V Stein, Guiying Cheng, Britt M Stockton, Brian P Fors, Eugene C Butcher, Ulrich H Von AndrianAbstract:Adhesion receptors that are known to initiate contact (tethering) between blood-borne leukocytes and their endothelial counterreceptors are frequently concentrated on the microvilli of leukocytes. Other adhesion molecules are displayed either randomly or preferentially on the planar cell body. To determine whether ultrastructural distribution plays a role during tethering in vivo, we used pre-B cell transfectants expressing L- or E-selectin ectodomains linked to transmembrane/intracellular domains that mediated different surface distribution patterns. We analyzed the frequency and Velocity of transfectant Rolling in high endothelial venules of peripheral lymph nodes using an intravital microscopy model. Ectodomains on microvilli conferred a higher efficiency at initiating Rolling than random distribution which, in turn, was more efficient than preferential expression on the cell body. The role of microvillous presentation was less accentuated in venules below 20 μm in diameter than in larger venules. In the narrow venules, tethering of cells with cell body expression may have been aided by forced margination through collision with erythrocytes. L-selectin transfected cells rolled 10-fold faster than E-selectin transfectants. Interestingly, Rolling Velocity histograms of cell lines expressing equivalent copy numbers of the same ectodomain were always similar, irrespective of the topographic distribution. Our data indicate that the distribution of adhesion receptors has a dramatic impact on contact initiation between leukocytes and endothelial cells, but does not play a role once Rolling has been established.
-
L-selectin–mediated Leukocyte Adhesion In Vivo: Microvillous Distribution Determines Tethering Efficiency, But Not Rolling Velocity
The Journal of experimental medicine, 1999Co-Authors: Jens V Stein, Guiying Cheng, Britt M Stockton, Brian P Fors, Eugene C Butcher, Ulrich H. Von AndrianAbstract:Adhesion receptors that are known to initiate contact (tethering) between blood-borne leukocytes and their endothelial counterreceptors are frequently concentrated on the microvilli of leukocytes. Other adhesion molecules are displayed either randomly or preferentially on the planar cell body. To determine whether ultrastructural distribution plays a role during tethering in vivo, we used pre-B cell transfectants expressing L- or E-selectin ectodomains linked to transmembrane/intracellular domains that mediated different surface distribution patterns. We analyzed the frequency and Velocity of transfectant Rolling in high endothelial venules of peripheral lymph nodes using an intravital microscopy model. Ectodomains on microvilli conferred a higher efficiency at initiating Rolling than random distribution which, in turn, was more efficient than preferential expression on the cell body. The role of microvillous presentation was less accentuated in venules below 20 μm in diameter than in larger venules. In the narrow venules, tethering of cells with cell body expression may have been aided by forced margination through collision with erythrocytes. L-selectin transfected cells rolled 10-fold faster than E-selectin transfectants. Interestingly, Rolling Velocity histograms of cell lines expressing equivalent copy numbers of the same ectodomain were always similar, irrespective of the topographic distribution. Our data indicate that the distribution of adhesion receptors has a dramatic impact on contact initiation between leukocytes and endothelial cells, but does not play a role once Rolling has been established.
