The kinetics of heterotypic aggregation following shear and fMLP stimulation.

Neutrophils (1 × 10⁶ cells/mL) and 300.19 cells (2 × 10⁶ cells/mL) were labeled, stimulated, and sheared as described in Figure 1. Aggregation was monitored as described in “Materials and Methods.” Heterotypic aggregation is presented as the percentage of total neutrophils bound to a 300.19 cell. Aggregation kinetics over a range of shear rates as denoted are plotted for the parent 300.19 cell line (A) and for transfected clones expressing ICAM-1 at (B) low levels (I_low) and (C) 8-fold higher levels (I_high). *P < .05 compared with peak aggregation at the same shear rate. Data are presented as mean ± SEM from 3 to 7 separate experiments.