Final answer:
A transfusion reaction is characterized by an immune response against foreign red blood cell antigens from incompatible blood, causing symptoms like fever, chills, and hemolysis, which can lead to severe consequences such as organ failure.
Step-by-step explanation:
A transfusion reaction occurs when a patient receives incompatible blood containing foreign red blood cell (RBC) antigens. If someone with type B blood receives type A blood, their anti-A antibodies will agglutinate the donor RBCs and activate the complement cascade, causing a strong inflammatory response alongside massive hemolysis. This could result in fever, chills, pruritus, urticaria, dyspnea, hemoglobinuria, and potentially severe hypotension, organ failure, and death.
Antigens on transfused RBCs that the immune system does not recognize as self can cause the immune system's leukocytes to mount a defense, producing antibodies that lead to the symptoms described. Importantly, with blood transfusions, blood group compatibility is crucial to avoid such reactions and the grave outcomes associated with it, including the occlusion of blood vessels in critical organs like the lungs and kidneys.
Additionally, erythroblastosis fetalis, another immune response to blood antigen incompatibility, demonstrates the importance of Rh factor matching in pregnancies. During the gestation of a subsequent child with an Rh-positive father, the Rh-negative mother's previously sensitized immune system might attack the fetus's RBCs, potentially causing severe anemia in the fetus, which requires medical intervention.