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

What characterizes hyperacute rejection of a transplanted organ?

1. Gradual loss of function over days

2. Immediate vascular thrombosis due to preformed antibodies

3. Cellular infiltration by T cells

4. Development of antibodies over weeks

The correct answer is: Immediate vascular thrombosis due to preformed antibodies

Hyperacute rejection of a transplanted organ is characterized primarily by immediate vascular thrombosis. This occurs because the recipient's immune system has preformed antibodies against the donor organ's antigens, which are often present on the endothelial cells of blood vessels in the transplanted tissue. Upon transplantation, these antibodies quickly bind to the antigens, leading to complement activation, inflammation, and ultimately rapid thrombosis of the graft's blood vessels. This response typically occurs within minutes to hours after transplantation, resulting in a swift and severe loss of function of the transplanted organ. In contrast, the other options describe features associated with different types of rejection. For instance, gradual loss of function over days indicates acute rejection or chronic rejection where the immune response develops more slowly rather than instantaneously. Cellular infiltration by T cells is indicative of acute cellular rejection, characterized by a delayed response that is mediated by the adaptive immune system. The development of antibodies over weeks pertains to chronic rejection or may refer to the process of sensitization that occurs before an acute response, neither of which aligns with the immediate nature of hyperacute rejection.