Anti–PECAM-1 antibodies promote platelet deposition on extracellular matrix. Two hundred fifty microliters of citrated whole blood was preincubated for 15 minutes at 37°C with either buffer alone or 5 μg/mL of normal mouse IgG1, PECAM-1.3, or PECAM-1.2. After 8 minutes of exposure to ECM-covered plates under conditions of low shear (200 s−1), samples were washed and stained and adherent platelets and aggregates were evaluated by image analysis as described in the Materials and Methods. Data are expressed as the percentage of ECM coverage (A) as well as average size (in square micrometers) of the aggregates formed (B). Note that both parameters were significantly increased (P = .017 andP = .02, respectively) in the presence of PECAM-1.2, but not PECAM-1.3.
