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.