HL-60 cell-cell interactions mediated by PMPs in new and old PPP.

HL-60 cells (total volume, 6 mL) were incubated with PMPs from freshly drawn blood (new PPP) or PMPs generated by aging PRP for 5 days (old PPP). HL-60 cells in the presence of PMPs were withdrawn over HL-60 cells prebound to an antihuman CD43 mAb-coated glass slide at 0.4 dyne/cm². The normalized rate of transient interactions of flowing HL-60 cells with prebound HL-60 cells was calculated by dividing the total number of transient interactions by the number of HL-60 cells on the surface and the duration of the experiment. No significant increase in the number of cell-cell interactions occurred with the addition of new PPP. *Indicates that significantly more cell-cell interactions occurred with the addition of old PPP (P < .001). The graph is representative of 5 independent experiments.