T-lymphocyte killing by T101-ricin A-chain immunotoxin: pH-dependent
potentiation with lysosomotropic amines
P Casellas, S Ravel, BJ Bourrie, JM Derocq, FK Jansen, G Laurent and P Gros
Department of Immunology, Sanofi-Recherche, Montpellier, France.
To maximize T-lymphocyte killing with anti-pan-T-lymphocyte immunotoxin
(IT), prepared by linking ricin A-chain to monoclonal antibody (MoAb) T101
(T101-RTA IT), we have established the nature and the extent of parameters
that influence the sensitivity of T lymphocytes to the IT. We showed that
peripheral blood T lymphocytes, which are much less susceptible than
malignant T cells to the T101-RTA IT, could become highly sensitive to the
IT when used in conjunction with NH4Cl. However, enhancement of the IT by
NH4Cl only occurred when the pH rose above neutrality. This pH-sensitive
process of IT activation by NH4Cl, which led to an all-or-nothing effect
within an extremely narrow pH window of 0.7 pH unit width, is due to the
fact that NH3 is the effective enhancing component of NH4Cl. We also showed
that F(ab')2 or Fab containing IT were much more effective than those
produced using the whole IgG counterpart. From these data, we defined a
procedure for an optimal and specific elimination of T lymphocytes in vitro
by treating them with (Fab)T101-RTA at 10(-8) mol/L at pH 7.8 in the
presence of NH4Cl for two hours. This peripheral blood cell processing
elicited an abrogation of three logs of functional T-cell response. Under
the same conditions, there was no reduction in the number of marrow
hematopoietic precursor granulocyte-macrophage colony-forming units
(CFU-GM).
Volume 72,
Issue 4,
pp. 1197-1202,
10/01/1988
Copyright © 1988 by The American Society of Hematology
