What is the main difference between hyperacute and acute rejection after transplantation?

What is the main difference between hyperacute and acute rejection after transplantation?

• A. Hyperacute is antibody-mediated and occurs within minutes to hours; acute involves T-cell and antibody mechanisms occurring days to weeks after transplant
• B. Hyperacute is T-cell mediated and occurs within days; acute is antibody-mediated within minutes
• C. Hyperacute occurs weeks after transplant; acute occurs within hours
• D. Hyperacute and acute are both antibody-mediated within minutes

Answer: (A)

The timing and the immune mechanism are what differentiate hyperacute from acute rejection. Hyperacute rejection happens almost immediately to a few hours after transplant and is driven by preformed recipient antibodies against donor antigens (such as ABO or HLA), with complement activation leading to rapid vascular injury and graft loss. Acute rejection occurs days to weeks after transplant and is primarily T-cell–mediated, as host T cells react against donor MHC antigens; there can be antibody-mediated components as well, but the cellular response is the key feature and occurs later. This matches the idea that hyperacute is antibody-driven and occurs within minutes to hours, while acute involves T-cell and possibly antibody mechanisms over days to weeks.

The timing and the immune mechanism are what differentiate hyperacute from acute rejection. Hyperacute rejection happens almost immediately to a few hours after transplant and is driven by preformed recipient antibodies against donor antigens (such as ABO or HLA), with complement activation leading to rapid vascular injury and graft loss. Acute rejection occurs days to weeks after transplant and is primarily T-cell–mediated, as host T cells react against donor MHC antigens; there can be antibody-mediated components as well, but the cellular response is the key feature and occurs later. This matches the idea that hyperacute is antibody-driven and occurs within minutes to hours, while acute involves T-cell and possibly antibody mechanisms over days to weeks.