Hemolytic activity of leukemic sera: the role of complement and sucrose

In sera of patients with acute myeloblastic leukemia (AML), hemolytic activity can be demonstrated in vitro in the presence of sucrose. To investigate the nature and the mode of action of this hemolytic activity, serum samples from 24 patients with AML were studied by incubation of normal human erythrocytes together with patient serum in the presence of sucrose at low ionic strength (inverse sucrose hemolysis test, ISHT). Fifty-five percent of the serum samples collected during the active stage of the disease gave a hemolysis rate of greater than 4%, whereas in remission only 15% of the samples lysed erythrocytes. Substitution of raffinose, lactose, or polyethylene glycol 400 for sucrose resulted in an almost complete failure of hemolysis under standard conditions, indicating a minor role of the low ionic strength in the ISHT. Heat inactivation, preincubation with inulin, and addition of EDTA, Mg2+-EGTA, or heparin completely abolished hemolytic activities of AML sera when the incubation was carried out for 30 minutes (standard conditions of the ISHT). A prolongation of the incubation time resulted in delayed hemolysis only with the Mg2+-EGTA-treated AML sera. The kinetics of this hemolysis by Mg2+-EGTA-treated AML sera were similar to those of normal human serum in the presence or absence of Mg2+-EGTA. Hemolysis was also obtained by performing the ISHT with normal sera and erythrocytes preincubated with AML sera. These observations suggest a mediation of membrane modification of normal human erythrocytes by AML sera in the presence of sucrose, resulting in an activation of the classical pathway of complement.