When a patient has been exposed to a high-frequency antigen, what issue may arise during transfusion?

The situation described involves exposure to a high-frequency antigen, which is a specific type of antigen that is present on the surface of red blood cells in a large portion of the population. When a patient who has been sensitized to such an antigen receives a transfusion of blood that contains that same antigen, an issue that may arise is an incompatible transfusion.

Incompatible transfusions can happen when the recipient's immune system recognizes the high-frequency antigen as foreign due to prior exposure, leading to the formation of antibodies against it. This immune response can result in the destruction of transfused red blood cells and potentially cause serious complications, including hemolytic reactions.

While unexpected hemolytic reactions and delayed transfusion reactions are potential consequences of incompatible transfusions, the fundamental issue revolves around the incompatibility itself resulting from the presence of anti-high-frequency antibodies in the patient’s serum. Additionally, minimal immune response is unlikely since the patient has already been exposed to the antigen and has developed antibodies. Hence, the primary concern during a transfusion in this context is the incompatibility due to these pre-existing antibodies against the high-frequency antigen.