Monoclonal antibody-mediated cytotoxicity of human myeloid leukemia cells:
an in vitro model for estimating efficiency and optimal conditions for
cytolysis
AL Howell and ED Ball
Monoclonal antibodies (MoAbs) to myeloid differentiation antigens have a
potential use in purging bone marrow of leukemia cells in autologous bone
marrow transplantation (ABMT) therapy for acute myelogenous leukemia (AML).
Because the efficiency of purging by MoAb and complement (C) is important
to the success of ABMT, we have designed an assay to determine optimal
conditions for leukemia cell lysis. In order to mimic the conditions of
remission bone marrow, normal buffy coat cells were mixed with cells from
the HL-60 promyelocytic leukemia cell line at a concentration that
approximated the normal-leukemia cell ratio found in remission marrow. The
cell mixture was treated at variable times and temperatures in the presence
of C and PM-81, an IgM MoAb that reacts with both normal granulocytes and
monocytes as well as with HL-60 cells. PM-81 binds to the majority of cells
from 90% of patients with AML yet does not react significantly with normal
stem cell populations. Because of the potential use of PM-81 in ABMT, it
seemed especially important to show that the antibody was capable of
mediating cytotoxicity of HL-60 cells in the presence of an excess of
antigen-positive cells. A clonogenic assay that permitted the growth of
HL-60 cell colonies but not normal progenitor cells in methylcellulose
cultures was used to measure the efficiency of HL-60 cell lysis. We found
that under certain conditions, PM-81 was capable of removing the small
percentage of HL-60 clonogenic cells admixed with normal buffy coat cells.
This information was useful for determining the optimal conditions for
purging bone marrow of leukemia cells for ABMT.
Volume 66,
Issue 3,
pp. 649-654,
09/01/1985
Copyright © 1985 by The American Society of Hematology
