Occurrence of disseminated intravascular coagulation in rat BNML leukaemia despite lack of leucocyte procoagulant activity

Signs of disseminated intravascular clotting were observed during the development of BNML myelomonocytic leukaemia in rats, when the peripheral leucocyte count exceeded 20,000/μl and more than 50% blasts were present in the circulation. BNML cells, harvested from blood and tested in appropriate systems, were found devoid of any precoagulant activity (PCA) even following prolonged in vitro incubation with endotoxin. Thus, it appears that these rat leukaemic cells share the same inability to express PCA which had been previously described in peripheral blood mononuclear cells from normal rats. Conceivably, in this rat model, leucocyte PCA does not respresent a major trigger of intravascular coagulation and blood clotting is initiated by other, mainly plasmatic, pathways.