Immune responses to transplants

Organ transplantation is the accepted and indeed the preferred treatment for most forms of end-stage organ failure. While the function of the immune system may be to protect against infection or "danger", the immune system, if not suppressed, also efficiently recognizes an organ transplant from a genetically disparate individual. This initiates an immune response, or an alloresponse, against the transplant. The alloimmune response involves adaptive and innate immune systems; T and B cells are the principle mediators of cellular and antibody-mediated rejection. Distinct immunologic and histologic differences exist between acute cellular, antibody mediated, and chronic rejection. Tolerance strategies include immunoregulation, costimulation blockade, and mixed chimerism; mechanisms of tolerance induction may differ from those that are needed to sustain it. Memory T cells are a significant barrier to tolerance induction. Identification of biomarkers for rejection and/or tolerance could initiate individualized immune modulation regimens.