Hyperacute graft rejection occurs after how much time?

Ans. a. 12 hoursRef: Robbins and Cotran Pathologic Basis of Disease 9th Ed; Page No. 233Hyperacute Graft RejectionOccurs within minutes to hoursDue to preformed antibodies due to transfusions, multiparity, or previous organ transplants (type II cytotoxic hypersensitivity)Antibodies bind to the grafted tissue and activate complement and the clotting cascade resulting in thrombosis and ischemic necrosisRare because of cross-matching blood, but common vignette.Acute Graft RejectionOccurs within days to weeks; the timing and mechanism are similar to a primary immune responseInduced by alloantigens (predominantly MHC) in the graftBoth CD4 and CD8 T cells play a role as well as antibodies (think normal immune response)Immunosuppressive therapy works to prevent this type of graft rejection mainly.Accelerated Acute Graft RejectionOccurs within days; the timing and mechanism are similar to a memory response.Chronic Graft RejectionOccurs within months to yearsPredominantly T cell mediatedDifficult to treat and usually results in graft rejectionEtiology not well understood, possibly triggered by viral infections