Clustered CD3/TCR complexes do not transduce activation signals after bispecific monoclonal antibody-triggered lysis by cytotoxic T lymphocytes via CD3.
Bispecfic mAb (bsmAb) directed against the CD3/TCR complex and a tumor-associated Ag (TAA) induces CTL-mediated lysis of TAA+ target cells. We have investigated whether bsmAb-pretargeted CTL can enter multiple lytic cycles. BsmAb-pretargeted CTL retained bsmAb-targeted lytic capacity for at least 24 h when exposed to medium without TAA+ target cells. Exposure of bsmAb-pretargeted CTL to TAA+ target cells resulted in a rapid loss of bsmAb-targeted cytotoxicity of TAA+ or Fc gamma R+ target cells, although the CTL retained surface bsmAb. Moreover, addition of rabbit anti-mouse lg to these CTL did not induce calcium mobilization. These CTL still showed Ag-specific cytotoxicity and cytolysis of anti-CD3 mAb-expressing hybridoma cells. Readdition of bsmAb to CTL that had lost bsmAb-targeted cytotoxicity instantly restored the bsmAb-targeted lytic activity of the CTL. Hence, as in Ag-specific cytolysis, bsmAb-pretargeted CTL can enter multiple bsmAb-targeted cytolytic cycles. Surprisingly, exposure of bsmAb-pretargeted CTL to Fc gamma R+ cells did not result in loss of bsmAb-targeted cytolysis of TAA+ cells. Fluorescence microscopic analysis revealed that bsmAb-mediated interaction with TAA+ cells, but not with Fc gamma R+ cells, resulted in clustering of bsmAb-pretargeted CD3/TCR complexes on the CTL surface. On the basis of the observed correlation between clustered bsmAb-pretargeted CD3/TCR complexes and loss of bsmAb-targeted cytotoxicity, we hypothesize that clustered CD3/TCR complexes can no longer transduce signals.
Department of Clinical and Tumor Immunology, Daniel den Hoed Cancer Center, Rotterdam, The Netherlands.
C J
CJ
Blank-Voorthuis
E
E
Braakman
C P
CP
Ronteltap
B C
BC
Tilly
E
E
Sturm
S O
SO
Warnaar
R L
RL
Bolhuis
D000911:Antibodies, Monoclonal / Q000276:immunology; D017252:CD3 Complex / Q000502:physiology*; D002478:Cells, Cultured; D003602:Cytotoxicity, Immunologic; D006801:Humans; D007111:Immunity, Cellular; D066298:In Vitro Techniques; D011940:Receptor Aggregation; D011948:Receptors, Antigen, T-Cell / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000276:immunology; D015398:Signal Transduction; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D013997:Time Factors
D000911:Antibodies, Monoclonal; D017252:CD3 Complex; D011948:Receptors, Antigen, T-Cell; D011993:Recombinant Fusion Proteins