Severe intravascular hemolysis is most likely caused by antibodies from which blood group system?

Severe intravascular hemolysis is primarily associated with antibodies from the ABO blood group system. This is due to the unique characteristics of the ABO antigens, which are present on red blood cells and can elicit a robust immune response if incompatible blood is transfused. When a person receives a transfusion of ABO incompatible blood, it can lead to the rapid destruction of red blood cells by the recipient's pre-existing antibodies. This process occurs in the intravascular space, leading to severe symptoms and complications.

In contrast, other blood group systems like Rh, Kell, and Duffy typically cause extravascular hemolysis. While these systems can also generate antibodies that lead to hemolytic reactions, the severity and rapid onset of intravascular hemolysis are most prominently linked to the ABO antibodies. ABO incompatibility's significance lies in the potential for acute hemolytic reactions, which can lead to serious morbidity and mortality. This makes the ABO blood group system critically important in blood transfusions and compatibility testing.