Abstract: Isolated ligands which bind a molecule expressed on the surface of T cells and induce antigen specific apoptosis in activated T cells are disclosed. Preferably, the T cell surface molecule is CTLA4 and the ligand is a monoclonal anti-CTLA4 antibody that binds to an epitope of CTLA4 distinct from the binding sites of B7-1 and B7-2. Upon binding of the antibody to CTLA4 on an activated T cell, in the presence of an antigenic signal, antigen specific apoptosis is induced. The invention also describes a novel natural CTLA4 ligand, distinct from B7-1 and B7-2, which mediates induction of apoptosis. Pharmaceutical compositions of anti-CTLA4 antibodies or other isolated CTLA4 ligands which can be administered to subjects to induce T cell apoptosis, thereby clonally deleting antigen specific T cells, such as alloreactive T cells in transplantation situations or autoreactive T cells in autoimmune disorders, are also disclosed.

Abstract: We teach a strategy to obtain large quantities of desired APCs, activated B cells, which are superior in their capacity to present tumor protein antigen in a multiadministration protocol. Human B cells can be obtained from peripheral blood in large numbers. These cells can be activated in vitro by coculture with CD40L (CD40-B cells) and an immunosuppressive agent such as cyclosporin A. They can expanded up to 1×103 to 1×104 fold in 2 weeks or 1×105 to 1×106 fold in 2 months. We demonstrate these cells are most efficient APCs comparable to DCs in stimulating allogeneic CD4+ CD45RA+, CD4+ CD45RO+, and CD8+ T cells. In contrast to DCs, CD40-B cells are fully functional even in the presence of immunosuppressive cytokines such as IL-10 and TGF?.

Abstract: Isolated ligands which bind a molecule expressed on the surface of T cells and induce antigen specific apoptosis in activated T cells are disclosed. Preferably, the T cell surface molecule is CTLA4 and the ligand is a monoclonal anti-CTLA4 antibody that binds to an epitope of CTLA4 distinct from the binding sites of B7-1 and B7-2. Upon binding of the antibody to CTLA4 on an activated T cell, in the presence of an antigenic signal, antigen specific apoptosis is induced. The invention also describes a novel natural CTLA4 ligand, distinct from B7-1 and B7-2, which mediates induction of apoptosis. Pharmaceutical compositions of anti-CTLA4 antibodies or other isolated CTLA4 ligands which can be administered to subjects to induce T cell apoptosis, thereby clonally deleting antigen specific T cells, such as alloreactive T cells in transplantation situations or autoreactive T cells in autoimmune disorders, are also disclosed.

Abstract: Isolated ligands which bind a molecule expressed on the surface of T cells and induce antigen specific apoptosis in activated T cells are disclosed. Preferably, the T cell surface molecule is CTLA4 and the ligand is a monoclonal anti-CTLA4 antibody that binds to an epitope of CTLA4 distinct from the binding sites of B7-1 and B7-2. Upon binding of the antibody to CTLA4 on an activated T cell, in the presence of an antigenic signal, antigen specific apoptosis is induced. The invention also describes a novel natural CTLA4 ligand, distinct from B7-1 and B7-2, which mediates induction of apoptosis. Pharmaceutical compositions of anti-CTLA4 antibodies or other isolated CTLA4 ligands which can be administered to subjects to induce T cell apoptosis, thereby clonally deleting antigen specific. T cells, such as alloreactive T cells in transplantation situations or autoreactive T cells in autoimmune disorders, are also disclosed.

Abstract: We teach a strategy to obtain large quantities of desired APCs, activated B cells, which are superior in their capacity to present tumor protein antigen in a multiadministration protocol. Human B cells can be obtained from peripheral blood in large numbers. These cells can be activated in vitro by coculture with CD40L (CD40-B cells) and an immunosuppressive agent such as cyclosporin A. They can expanded up to 1×103 to 1×104 fold in 2 weeks or 1×105 to 1×106 fold in 2 months. We demonstrate these cells are most efficient APCs comparable to DCs in stimulating allogeneic CD4+ CD45RA+, CD4+ CD45RO+, and CD8+ T cells. In contrast to DCs, CD40-B cells are fully functional even in the presence of immunosuppressive cytokines such as IL-10 and TGF&bgr;.