Monoclonal antibodies against T cell receptor/CD3 complex induce cell death of Th1 clones in the absence of accessory cells.

We have used anti-T cell mAbs as mimic ligands to study the effects of TCR/CD3 ligation of Th1 clones in the presence or absence of accessory cells. Our results demonstrated that ligation of TCR/CD3 in the presence of accessory cells induces proliferation of Th1 clone, while the same ligation in the absence of accessory cells results in death. This effect is inhibited by cyclosporin A and by anti-IFN-gamma mAbs and is restored by adding exogenous recombinant IFN-gamma tb CsA treated cells. We propose a model which could provide a general framework to explain activation, clonal anergy as well as clonal deletion of T lymphocytes during thymic development and in the peripheral.