Different susceptibilities of normal T cells and T cell lines to immunotoxins.
In the context of ex vivo T cell elimination from bone marrow, the anti-T cell cytotoxic potential of immunotoxins (IT) prepared by conjugation of the monoclonal antibodies (MoAb) WT32 (CD3), T101 (CD5), and WT1 (CD7) to ricin A chain was evaluated. The cytotoxicity of IT was based on protein synthesis inhibition in human T cell lines: GH1, CEM, HPB-ALL, and Jurkat, and appeared closely related to the antigen density and internalization rate of and appeared closely related to the antigen density and internalization rate of the IT. Normal unstimulated T cells appeared to be rather insensitive to IT not due to a low antigen density or decreased internalization. The cytotoxicity of IT to T cells could be enhanced considerably by NH4Cl. Treatment of T cells with a cocktail of IT (10(-8) M) and 20 mM NH4Cl resulted in a 5000-fold cytoreduction as measured by clonogenic assays of limiting T cell dilutions, whereas the haematopoietic progenitor cells remained unaltered. Stimulation of T cells with phytohaemagglutinin (PHA) prior to incubation with IT considerably increased the sensitivity to IT treatment. Thus, normal T cells are less sensitive to anti-T cell IT than T cell lines and activated T cells. This suggests that a low protein synthesis is responsible for the resistance to IT. However, a high specific cytotoxicity of IT to normal T cells can be achieved in the presence of 20 mM ammonium chloride.
Preijers
F W
FW
Department of Haematology, University Hospital Nijmegen, The Netherlands.
Tax
W J
WJ
Wessels
J M
JM
Capel
P J
PJ
De Witte
T
T
Haanen
C
C
D000643:Ammonium Chloride / Q000494:pharmacology; D000911:Antibodies, Monoclonal; D000945:Antigens, Differentiation, T-Lymphocyte / Q000276:immunology; D001854:Bone Marrow Cells; D002460:Cell Line; D004306:Dose-Response Relationship, Immunologic; D006412:Hematopoietic Stem Cells / Q000187:drug effects / Q000276:immunology; D006801:Humans; D000922:Immunotoxins / Q000494:pharmacology*; D066298:In Vitro Techniques; D010835:Phytohemagglutinins / Q000494:pharmacology; D012276:Ricin / Q000008:administration & dosage; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology*
D000911:Antibodies, Monoclonal; D000945:Antigens, Differentiation, T-Lymphocyte; D000922:Immunotoxins; D010835:Phytohemagglutinins; D000643:Ammonium Chloride; D012276:Ricin