Platelet binding in mononuclear cell preparations from peripheral blood.

We have investigated the relative binding affinity of white blood cells for platelets, during the centrifugation and washing procedures used for separating mononuclear cells from peripheral blood. In wet cell preparations the majority of monocytes (greater than 90%) showed platelet binding, compared to 14% of lymphocytes and 38% of polymorphs. Monocytes also had greater numbers of attached platelets per cell and demonstrated considerable variation in their affinity for platelets. The phenomenon was affected by the calcium concentration of the medium. Our observations are of value for identifying monocytes in wet cell preparations. The technique may also be useful for studying platelet adhesion in vascular disease.