Graft versus host disease

Graft-versus-host disease is a common complication of allogeneic bone marrow transplantation. After bone marrow transplantation, T cells that were present in the transplanted cell population, either as contaminants or intentionally introduced into the host, attack the tissues of the transplant recipient. Graft-versus-host disease can occur even when HLA-identical sibling are the donors. HLA-identical siblings or HLA-identical unrelated donors (called a minor mismatch as opposed to differences in the HLA antigens, which constitute a major mismatch) often still have genetically different proteins that can be presented on the MHC-antigen surveillance system that protects the body from foreign invaders.

While donor T-cells are undesirable as effector cells of graft-versus-host-disease, they are valuable for engraftment by preventing the recipient's residual immune system from rejecting the bone marrow graft. Additionally, as bone marrow transplantation is frequently used to cure maligant disorders (most prominently the