The infusion of the donor allograft (referred to as "day 0") is usually performed 1-2 days following the completion of the conditioning regimen.The allograft consists of not only donor hematopoietic stem cells but also immune cells (including NK, B, and T-cells) that were eradicated in the patient by the conditioning regimen. Patients typically receive immunosuppressive drugs, such as cyclosporine (CSA), or tacrolimus, for the first 3-6 months following the procedure to prevent the donor immune cells from attacking normal host tissues, such as the liver, GI tract, or skin, a complication known as graft-versus-host disease (GVHD).