Rolling of IRBC on immobilized soluble P-selectin in the presence of NRS, G1, a MoAb that inhibits neutrophil rolling on P-selectin, and an anti–P-selectin polyclonal Ab. Immobilized P-selectin was preincubated with each of the Ab at the concentrations indicated at 37°C for 30 minutes. The same concentration of Ab was maintained in the perfusate. Values represent the mean number of rolling cells ± SEM of 10 clinical P falciparum isolates studied.