The efficacy of CD3 x CD19 bispecific monoclonal antibody (BsAb) in a
clonogenic assay: the effect of repeated addition of BsAb and interleukin-2
IA Haagen, AJ Geerars, WB de Lau, BJ Bast and BC de Gast
Department of Immunology and Hematology, University Hospital of Utrecht,
The Netherlands.
To evaluate the potency by which human T cells are targeted and activated
by bispecific monoclonal antibodies (BsAbs) to lyse tumor cells, a
clonogenic assay was developed. The efficacy of a CD3 x CD19 BsAb binding
to both the CD3 T-cell antigen and the CD19 B-cell antigen was already
proven in 51Cr-release assays and in 3-day activation cultures. To achieve
more quantitative results, a 14-day clonogenic assay, based on
limiting-dilution, was performed for the determination of the initial and
residual number of clonogenic units obtained with a CD19+ pre-pre-B acute
lymphoblastic leukemia (ALL-B) cell line. Elimination of up to 5 logs of
ALL-B cells by freshly isolated peripheral blood mononuclear cells (PBMCs)
cultured with BsAb plus interleukin-2 (IL-2) could be detected. The
presence of human IgG did not abolish the effect. Repeated addition of each
of the two agents was necessary, because a single treatment produced only a
1- to 2-log kill. CD3 monoclonal antibody and IL-2 stimulation
("lymphokine-activated killer cell" conditions) resulted in only a 2-log
kill. The number of T cells proved critical in lysis of ALL-B cells, with a
5-log kill using a T-cell:B-cell ratio of 3:1 but with only a 1-log kill
using a ratio of 1:1. PBMCs isolated from patients with non-Hodgkin's
lymphoma, both in relapse or remission, proved to be as competent as those
from healthy donors in removing ALL-B cells. This clonogenic assay shows
the importance of repeated administration of CD3 x CD19 BsAb and IL-2 and
offers the possibility to compare it with other therapies in B-cell
malignancy.
Volume 85,
Issue 11,
pp. 3208-3212,
06/01/1995
Copyright © 1995 by The American Society of Hematology
