Rabbit-derived anti-human thymocyte globulin (rATG) is a gamma globulin preparation obtained from hyperimmune serum of rabbits immunized with human thymocytes. rATG has been used predominately in solid organ transplant immunosuppressive regimens. rATG is a predominantly lymphocyte-specific immunosuppressive agent. It contains antibodies specific to the antigens commonly found on the surface of T cells. After binding to these surface molecules, rATG promotes the depletion of T cells from the circulation through mechanisms which include opsonization and complement-assisted, antibody-dependent, cell-mediated cytotoxicity. The plasma half-life ranges from 1.5 12 days. rATG is administered intravenously at a dose of 0.5 mg/kg recipient body weight on day -6 and at a dose of 1.0 mg/kg recipient body weight on days -5, -4, -3, -2, and -1. Unlike equine ATG, rabbit ATG does not require a pre-infusion skin test to check for hypersensitivity. Methylprednisolone 250 mg will be given before every dose of rATG. Additional medications such as diphenhydramine may be given at the discretion of the attending physician. Although rare, the major toxicity is anaphylaxis; chills, fever, pruritus or serum sickness may occur.