... the down-regulation of Tcell responses. Its inhibition may restrict T cell activationduring both the initiation and progression of the antitu-mor response. Thus, blockade of CTLA-4 inhibitory ... second is the binding of costimulatory ligands, expressed on APC, to receptors on the T cells. The discovery of multiple costimulatorymolecules that influence the course of T cell activation ... anti-CTLA-4 Ab alone or in combination withother modalities to treat murine tumors. Activation of vas-culature in tumors, extravasation and proliferation of Tcells, and increased ratios of Teff/Treg...