Transplantation of hematopoietic stem cells is a successful therapy for some tumors derived from bone marrow precursors, such as certain leukemias and lymphomas, and it can be used to cure some primary immunodeficiencies and inherited hematopoietic stem-cell diseases. One of the major complications of allogeneic bone marrow transplantation is graft-versus-host disease (GVHD), in which mature donor T cells that contaminate the allogeneic bone marrow recognize the tissues of the recipient as foreign, causing a severe inflammatory disease characterized by rashes, diarrhea, and liver disease. GVHD is particularly virulent when there is a mismatch of a major major histocompatibility complex (MHC) class I or class II antigen. Most transplants are therefore undertaken only when the donor and recipient are HLA-matched sibs or, less frequently, when there is an HLA-matched unrelated donor. However, GVHD also occurs in the context of disparities between minor histocompatibility antigens, and immunosuppression must be used in every stem-cell transplant (summary by Janeway et al., 2005).
At the core of the immunogenetic basis for GVHD is the diversity of HLA, killer immunoglobulin-like receptors (KIRs; see 604936), and cytokine genes. HLA class I molecules function as ligands for natural killer cell inhibitory KIRs, indicating that GVHD results from a complex interplay between innate and adaptive immune responses. Cytokines may modulate the intensity of tissue injury and inflammation in GVHD, and therefore cytokine polymorphisms in either patient or donor or both may explain individual risks of GVHD (review by Petersdorf and Malkki, 2006). [from
OMIM]