From the Guidelines
Hyperacute rejection is indeed antibody mediated, making option (a) correct. Hyperacute rejection occurs immediately or within minutes to hours after transplantation when preformed antibodies in the recipient's circulation recognize antigens on the donor organ's vascular endothelium, as described in 1. This triggers complement activation, leading to rapid thrombosis, ischemia, and necrosis of the graft.
Key Points to Consider
- Option (b) is incorrect because hyperacute rejection cannot be reversed with steroids; once initiated, it typically results in immediate graft loss requiring removal, as noted in 1.
- Option (c) is incorrect as acute rejection is primarily T cell mediated, not B cell mediated, with T cells recognizing foreign HLA molecules and initiating cellular damage to the graft, a concept supported by the understanding of immune responses in transplantation 1.
- Option (d) is incorrect because acute rejection typically occurs within days to weeks after transplantation, not over months, highlighting the importance of early detection and management, as discussed in 1.
Clinical Implications
Understanding these mechanisms is crucial for transplant management, as hyperacute rejection requires prevention through cross-matching before transplantation, while acute rejection can often be treated with immunosuppressive therapy if detected early, emphasizing the need for vigilant monitoring and timely intervention, as recommended in 1. The use of cardiac imaging, as suggested in 1, can play a significant role in assessing and following patients after heart transplantation, aiding in the early detection of complications such as graft rejection.
From the Research
Graft Rejection Mechanisms
- Hyperacute rejection is indeed antibody-mediated, as stated in studies 2, 3, 4
- Hyperacute rejection is not typically reversed with steroids, as antibody-mediated rejection does not respond to conventional anti-rejection therapy, including steroids 2
- Acute rejection is not solely B cell mediated, as it involves both antibody-mediated and T-cell mediated mechanisms 3, 5
- Acute rejection does not necessarily occur over a month, as it can occur at any time post-transplantation, depending on various factors such as donor-specific antibodies and immunosuppressive regimes 4, 6
Rejection Types and Mechanisms
- Hyperacute rejection is a severe form of antibody-mediated rejection that occurs shortly after transplantation 2, 4
- Acute antibody-mediated rejection is a significant cause of graft loss and is associated with worse graft outcomes 4, 6
- Chronic antibody-mediated rejection is a major contributor to graft loss in the late posttransplant phase and is characterized by distinct pathologic lesions 3, 5, 6