Hyperacute graft rejection is seen within

(A) 24 hoursTRANSPLANT REJECTION TypeOnsetMechanism & Vessel HistologyType of HypersensitivityHost vs GraftHyperacuteImmediatePreformed antibodies directed against the donor tissue. Caused by accidental ABO blood type incompatibility which is very rare. Presents while still in surgery with thrombosis and occlusion of graft vessels.II AcuteWeeks to monthsT-cell mediated immune response directed against the foreign MHC. Inflammation & leukocyte infiltration of graft vessels results. Most common typeIV ChronicMonths to yearsT-Cell mediated process resulting from the foreign MHC 'looking like' a self MHC carrying an antigen. Results in intimal thickening & fibrosis of graft vessels as well as graft atrophy.III & IVGraft vs HostVariesDonor T-cells in the graft proliferate and attack the recipient's tissue. Most commonly seen in bone marrow transplants. Presents with diarrhea, rash & jaundice.IVThe most important thing to remember is the time-frame for the onset of symptoms as you can often determine what type of rejection it is based on time alone.[?]Hyperacute Rejection:oThis form of rejection occurs within minutes or hours after transplantation & can be recognized by the surgeon soon after the graft vasculature is anastomosed to the recipient's.oHyperacutely rejecting kidney rapidly becomes cyanotic, mottled & flaccid and may excrete few drops of bloody urine.oThis form of rejection is due to the presence of preformed antidonor Ab's in the host circulation.oThis form of rejection is rarely seen in today's practice.Hyperacute Transplant Rejection Antibody-Mediated Type II Hypersensitivity ReactionHyperacute Transplant Rejection Antibody-Mediated Type II Hypersensitivity ReactionMost dramatic form of tissue incompatibility, begins within minutes to hours.Blood Group Antigens are expressed by endothelial cells of blood vessels (solid vascularized organs).Antibodies (IgM) - Complement Fixation - Neutrophil, Platelet activation - Intravascular consulation - Irreversible Ischemic Necrosis. Cannot be reversed, should be avoided.Today, Hyperaucte rejection by anti-ABO antibodies is extremely rare. HLA I is expressed on vascular endothelium cells, preexisting antibodies (IgG) against HLA class I variants can also cause hyperacute rejection.[?]Transplant Rejection Mechanism[?]Antibody-Mediated Reactions:[?]Ab's produced against donor Ag can also mediate rejection through two forms:oHyperacute rejection: Immediate rejection soon after transplantation.-Occurs when preformed antidonor Ab's are present in the circulation of the recipient.