Role of CD11/CD18 in shear rate-dependent leukocyte-endothelial cell interactions in cat mesenteric venules.
In vivo microscopy was used to assess the relationships among shear rate (and shear stress), leukocyte rolling velocity, and leukocyte adherence in a cat mesentery preparation. Shear rate in individual venules and arterioles of 25-35 microns diameter were varied over a wide range by graded occlusion of an arterial loop. There was a linear decline in leukocyte rolling velocity (Vwbc) as red cell velocity (Vrbc) was reduced. The ratio Vwbc/Vrbc remained constant despite variations in shear stress from 5-25 dyn/cm2. A reduction in shear stress was associated with an increased leukocyte adherence, particularly when Vwbc was reduced below 50 microns/s. Reduction in wall shear rate below 500 s-1 in arterioles allowed 1-3 leukocytes to adhere per 100 microns length of vessel, while venules exposed to the same shear rates had 5-16 adherent leukocytes. In arterioles, leukocyte rolling was only observed at low shear rates. At shear rates less than 250 s-1 leukocyte rolling velocity was faster in arterioles than venules, and the ratio Vwbc/Vrbc for arterioles was 0.08 +/- 0.02, which was fourfold higher than the ratio obtained in venules at similar shear rates. Pretreatment with the CD18-specific antibody (mAb) IB4 increased leukocyte rolling velocity in venules by approximately 20 microns/s at red cell velocities below 2,000 microns/s. mAb IB4 largely prevented the leukocyte adherence to arterioles and venules, and increased the ratio Vwbc/Vrbc observed in venules at low shear elicit a CD18-dependent adhesive interaction between leukocytes and microvascular endothelium, and that differences in shear rates cannot explain the greater propensity for leukocyte rolling and adhesion in venules than arterioles.
Perry
M A
MA
School of Physiology & Pharmacology, University of New South Wales, Kensington, Australia.
Granger
D N
DN
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000943:Antigens, Differentiation / Q000502:physiology*; D001160:Arterioles / Q000166:cytology; D018845:CD11 Antigens; D018821:CD18 Antigens; D002415:Cats; D002448:Cell Adhesion; D004730:Endothelium, Vascular / Q000166:cytology*; D004912:Erythrocytes / Q000502:physiology; D007962:Leukocytes / Q000502:physiology*; D008642:Mesenteric Veins; D008833:Microcirculation / Q000166:cytology*; D016028:Receptors, Leukocyte-Adhesion / Q000502:physiology*; D013314:Stress, Mechanical
D000911:Antibodies, Monoclonal; D000943:Antigens, Differentiation; D018845:CD11 Antigens; D018821:CD18 Antigens; D016028:Receptors, Leukocyte-Adhesion