A ricin A chain-containing immunotoxin that kills human T lymphocytes in
vitro
PJ Martin, JA Hansen and ES Vitetta
An immunotoxin specific for human T lymphocytes was prepared by coupling an
IgG2a anti-CD3 murine monoclonal antibody (64.1) to purified ricin A chain
(64.1-A). Treatment of blood mononuclear cells with this immunotoxin at a
concentration of 1.7 X 10(-9) mol/L for two hours at 37 degrees C in the
presence of 20 mmol/L NH4Cl decreased phytohemagglutinin-stimulated protein
synthesis by 95%. In addition, a sensitive culture assay showed that fewer
than 0.03% T cells remained after treatment of human bone marrow
mononuclear cells with 64.1-A at a concentration of 1.7 X 10(-9) mol/L. The
inhibition of protein synthesis could be prevented by preincubating cells
with unconjugated 64.1 antibody but not by preincubating cells with a
control IgG2a antibody that binds to a different T cell antigen (CD5). At
concentrations up to 1 X 10(-8) mol/L, 64.1-A had little effect on blood
mononuclear cells from baboons or human myeloid precursors (CFU- GM), which
do not express the CD3 antigen recognized by 64.1. Taken together, these
results indicate that the toxicity of 64.1-A was specific and that 64.1-A
may be a useful reagent for depleting T cells from donor marrow as a means
of preventing acute graft-v-host disease after allogeneic bone marrow
transplantation.
Volume 66,
Issue 4,
pp. 908-912,
10/01/1985
Copyright © 1985 by The American Society of Hematology
