Two strategies are promising: Blockade of T-cell costimulatory pathways using a cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) - IgG1 fusion protein Induction of chimerism (coexistence of donor and recipient immune cells, which may allow graft tissue to be recognized as self) using nonmyeloablative pretransplantation treatment (eg, with cyclophosphamide, thymic irradiation, ATG, and cyclosporine) to induce transient T-cell depletion, engraftment of donor hematopoietic stem cells, and subsequent tolerance of solid organ transplants from the same donor (under study) Table Posttransplantation Complications Complications include the following: Rejection Infection Renal insufficiency Cancer Atherosclerosis Rejection Rejection of solid organs may be hyperacute, accelerated, acute, or chronic (late).