Hyperacute Rejection: Occurs within minutes to hours after transplantation and is usually due to pre-existing antibodies in the recipient against donor antigens. Acute Rejection: Typically occurs within the first few weeks to months post-transplant. It is mediated by T-cells and can be reversible if detected early. Chronic Rejection: Develops over months to years and involves gradual loss of organ function due to long-term immune response and fibrosis.
