Elastase activity in leukaemic cells and plasma in patients with acute leukaemia.

Proteolysis of coagulation factors and inhibitors resulting in haemorrhage can be mediated by elastase. Indirect signs of this are elevated levels of elastase complexed to its inhibitor in plasma, alpha 1-antitrypsin (E alpha 1-AT). We have measured intracellular elastase activity in leukaemic cells from 60 patients with acute leukaemia. Elastase activity was detected in 92% of the patients with acute nonlymphoblastic leukaemia (ANL), no activity was found in the patients with acute lymphoblastic leukaemia (ALL). High levels were found in cells from patients with promyelocytic leukaemia. Moderate to high total circulating blast elastase activity was measured in 70% of the ANL patients with haemorrhage compared with 36% of the patients without bleeding complications (p < 0.05). The available intracellular elastase activity was correlated to the level of E alpha 1-AT (rs = 0.42, p < 0.01) but not to the elastase specific split product of fibrinogen, B beta 30-43. In complete remission the levels of E alpha 1-AT were normalized. Intracellular elastase activity might be a useful supplement to differentiate ANL and ALL.