Aggregation of NB-4 cells in the presence of PMA or activating MoAb KIM 185. (A) The effect of PMA (50 ng/mL) and KIM 185 (10 μg/mL) on the aggregation of NB-4 cells and NB-4 cells exposed to 100 nmol/L tRA for 72 hours is shown. Aggregation was measured at 6 hours as described in Materials and Methods The histogram depicts the percent aggregation ± SD. The combination of modulators added to the assay are indicated on the x-axis. Data represent results from three separate experiments performed in duplicate. (B) Kinetics of NB-4 cell adhesion after exposure to 100 nmol/L tRA for 72 hours. Cells were washed and then allowed to aggregate in the presence of tRA (tRA), absence of tRA (tRA washed), or tRA and 50 ng/mL PMA (PMA). The percent aggregation at different time points was determined. Data represents results from three separate experiments performed in duplicate.