Cytotoxic T Lymphocyte Antigen 4-Immunoglobulin Fusion Protein Combined With Methotrexate/Cyclosporine as Graft-Versus-Host Disease Prevention in a Canine Dog Leukocyte Antigen-Nonidentical Marrow Transplant Model1

BACKGROUND: We studied whether blocking of the T cell costimulatory signal from B7-->CD28 by cytotoxic T lymphocyte antigen 4-immunoglobulin fusion protein would, either by itself or when added to methotrexate/cyclosporine, result in improved graft-versus-host disease prevention after dog leukocyte antigen nonidentical canine hematopoietic stem cell transplantation after 920 cGy total body irradiation. RESULTS AND CONCLUSIONS: Survivals of cytotoxic T lymphocyte antigen 4-immunoglobulin fusion protein-treated dogs were only slightly prolonged over controls. It appeared that the addition of cytotoxic T lymphocyte antigen 4-immunoglobulin fusion protein failed to induce graft-host tolerance in this model beyond that achieved with methotrexate/cyclosporine alone.