American Board of Surgery Qualifying Exam (ABS QE) Practice Test

What characterizes accelerated rejection in transplant patients?

1. Decreased T-cell activation

2. Presensitized T cells to donor HLA

3. Reduced antibody production

4. Increased histamine levels

The correct answer is: Presensitized T cells to donor HLA

Accelerated rejection in transplant patients is primarily characterized by the presence of presensitized T cells to donor HLA (human leukocyte antigen). This phenomenon occurs when a recipient has previously been exposed to donor antigens, either through prior transplants or blood transfusions, which can lead to a rapid immune response upon re-exposure to the same donor tissues. In this situation, the memory T cells that recognize the donor HLA are already present in the recipient’s immune system, allowing for a quicker and more robust activation of the immune response. This results in an accelerated rejection of the transplanted organ, typically occurring within days rather than weeks to months as seen in acute rejection scenarios where T-cell activation happens de novo. The other options do not accurately describe the mechanisms involved in accelerated rejection. Decreased T-cell activation contradicts the principles of accelerated rejection, where the activation is increased due to the presence of memory T cells. Reduced antibody production is also not characteristic of this phenomenon, as antibody-mediated responses can contribute to the rejection process. Increased histamine levels relate more to allergic reactions and are not directly involved in the transplant rejection processes. Thus, presensitized T cells recognizing the donor HLA is the critical element leading to accelerated rejection.