Leukocytes and Thrombosis

SummaryWhite blood cells can no longer be considered simple trapped inclusions within thrombi. Their numbers in thrombi relative to blood counts increase with time. They appear to come from the blood flowing past the thrombus. They appear to migrate by amoeboid movement into the thrombic mass. Polymorphonuclear neutrophils have been shown to be lytic to fibrin and other proteins and thus can contribute to thrombus dissolution. There is increasing evidence that neutrophils may impart important cytotrophic function to proliferating cells during thrombus organization. Eosinophils are known to carr profibrinolysin and will release this precursor at sites of fibrin deposition. Mononuclear leukocytes can transform into fibroblasts in tissue culture and I consider a thrombus an ideal tissue culture medium. All of these cells can contribute to thrombus dissolution simply by mechanical weakening of the mass by migration into it, releasing enzymes, and allowing blood flow to carry away pieces of the thrombus as emboli. I extend my perspective on thrombosis by considering these intravascular solids as cell tissue cultures rather than simple blood clots or platelet aggregates.