Myosin-disruption prevents CD43-mediated cell aggregation. (A) T lymphoblasts were pretreated during 30 minutes with 20 mmol/L of butanedione monoxime. Cells were then allowed to adhere to FN80 in the presence of the proaggregatory anti-CD43 HP2/21 MoAb. Cells were filmed with a time-lapse videocassete recorder for 10 hours. Note the lack of cell polarization and aggregation in the first 2 hours recorded. White arrowheads point to cellular uropods displayed by cells after 9 hours of anti-CD43 treatment. (B) T lymphoblasts were incubated for 30 minutes at 37°C in the presence of 10 mmol/L butanedione monoxime (▪), 20 μmol/L colchicine (▴), or 20 μmol/L cytochalasin D (⧫) or in the absence of any cytoskeletal drug (•), before the addition of anti-CD43 HP2/21 MoAb. The percentage of aggregation was calculated at different times as described in the Materials and Methods.