Sensitivity of CD98-induced aggregation to blocking antibodies added at different times.

U937-cell aggregation was measured under standard conditions in the presence of CD98-AHN-18 (1.5 μg/mL). Antibodies to CD29 (MAR4, 0.5 μg/mL), CD98 (BU89, 1.2 μg/mL), CD147 (MEM M6/1, 1.6 μg/mL), and CD18 (CLB-LFA1, 1.5 μg/mL) were added to the culture before, together with, or after the aggregating antibody as shown. Results are expressed as percentage of aggregation relative to the aggregation in the absence of blocking antibody (column labeled 0 in each panel). Means that differ significantly from control (absence of inhibitory antibody,P < .05) are shown with an asterisk.