PLATELET SATELLITISM AND ALPHA-GRANULE PROTEINS

Blood smears from a patient with severe generalised arteriopathy and an occluded synthetic femoropopliteal graft showed the phenomenon of EDTA dependent adherence of platelets to neutrophils (platelet satellitism). Immunoenzymatic staining with a monoclonal antibody to thrombospondin showed that adherence to neutrophils exclusively involved platelets that stained strongly positive for thrombospondin, while negative or weakly positive platelets showed no tendency to adhere. There was no increase in platelet surface immunoglobulins. This suggests a possible role for thrombospondin or some other cytoadhesive platelet alpha-granule protein in mediating the adherence of platelets to neutrophils in cases of satellitism.