Binding and inhibition of CD24-transfected A125 adenocarcinoma cell versus nontransfected cells to human platelets. (A) PMA-activated platelets were adsorbed to 96-well tissue culture plates at 37°C for 1 hour. Europium-labeled tumor cells (A125 v A125-CD24) were adjusted to 106/mL and equal numbers of cells were allowed to bind. Note that the Eur3+ labeling of both types of cells was similar. (B) PMA-activated platelets were adsorbed to 96-well tissue culture plates at 37°C for 1 hour. Europium-labeled tumor cells A125 and A125-CD24 were allowed to bind in the absence or presence of the indicated antibodies or 2 μg/mL soluble CD24 or HSA, respectively. Bound and nonbound cells were separated by buoyant density as described in Materials and Methods. After fixation of bound cells the Europium fluorescence was measured and the results are expressed in percent inhibition of the added compound relative to medium control. Three independent experiments with similar results were performed for (A) and (B) and one representative experiment is shown.
