Effect of neuraminidase and proteases on IRBC rolling on immobilized soluble P-selectin. A 5% suspension of IRBC was treated with 1 U/mL of neuraminidase from Arthrobacter ureafaciens for 1 hour at 37°C. Control IRBC were incubated in buffer alone (mock neuraminidase). IRBC were also treated with 100 μg/mL of TPCK-treated trypsin and TLCK-treated chymotrypsin at 37°C for 30 minutes. Values represent the mean number of rolling cells ± SEM for 5 clinical P falciparum isolates studied.