Onset: Months to years

CD4+ T cells respond to recipient APCs presenting donor peptides, including allogeneic MHC. Both cellular and humoral components (type II and IV hypersensitivity reactions).

Features:- Recipient T cells react and secrete cytokines → proliferation of vascular smooth muscle, parenchymal atrophy, interstitial fibrosis. Dominated by arteriosclerosis.- Bronchiolitis obliterans (lung)- Accelerated atherosclerosis (heart)- Chronic graft nephropathy (kidney)- Vanishing bile duct syndrome (liver)