Kinetics and strength of β2-integrin receptor–ligand interactions. Neutrophils (3 × 106cells/mL) and E3-ICAM (5 × 106 cells/mL) cells were stimulated with 1 μmol/L FMLP and sheared in a cone-plate viscometer over a range of shear rates from 100 to 500 s−1 in normal HEPES buffer (media viscosity, =0.7 cp, A and B) or on addition of 6% Ficoll to the HEPES buffer (media viscosity, =1.7 cp, C and D). (A) Percent neutrophils in heterotypic aggregates in normal buffer. (B) Adhesion efficiencies for neutrophil–E3-ICAM collisions were computed from data presented in A, and compared with the adhesion efficiency for neutrophil-neutrophil collisions in independent homotypic aggregation experiments in the presence of 30 μg/mL anti–L-selectin MoAb, LAM1-3 Fab. (C) Percent neutrophils in heterotypic aggregates in HEPES buffer with 6% Ficoll. (D) Adhesion efficiencies for neutrophil–E3-ICAM were computed for the data in C and compared with neutrophil-neutrophil aggregation in the presence of LAM1-3 in media with viscosity 1.7 cp. Error bars represents SEM from three to eight independent experiments. *P < .05 with respect to neutrophil–E3-ICAM adhesion in the absence of Ficoll.
