Which incompatibility is not associated with intravascular hemolysis?

Which incompatibility is not associated with intravascular hemolysis?

• A. ABO
• B. Rh
• C. Minor antigen
• D. None of the above

Answer: (B)

The key idea is how antibodies cause red cell destruction during a transfusion. Intravascular hemolysis happens when donor red cells are attacked by antibodies that strongly fix complement directly in the bloodstream. ABO mismatches are the classic example because the recipient’s anti-A or anti-B antibodies are typically IgM and activate complement vigorously, shredding red cells inside vessels. Rh incompatibility, on the other hand, usually involves IgG antibodies against the D antigen. These antibodies bind the red cells and are cleared mainly by macrophages in the spleen and liver, leading to extravascular hemolysis rather than rapid destruction within the vessels. Minor antigen incompatibilities (like Kell, Duffy, Kidd) are also typically IgG and cause extravascular hemolysis rather than intravascular damage, though rare cases can involve intravascular mechanisms. So, Rh incompatibility is not associated with intravascular hemolysis in the typical transfusion reaction scenario, making it the best answer.

The key idea is how antibodies cause red cell destruction during a transfusion. Intravascular hemolysis happens when donor red cells are attacked by antibodies that strongly fix complement directly in the bloodstream. ABO mismatches are the classic example because the recipient’s anti-A or anti-B antibodies are typically IgM and activate complement vigorously, shredding red cells inside vessels.

Rh incompatibility, on the other hand, usually involves IgG antibodies against the D antigen. These antibodies bind the red cells and are cleared mainly by macrophages in the spleen and liver, leading to extravascular hemolysis rather than rapid destruction within the vessels. Minor antigen incompatibilities (like Kell, Duffy, Kidd) are also typically IgG and cause extravascular hemolysis rather than intravascular damage, though rare cases can involve intravascular mechanisms.

So, Rh incompatibility is not associated with intravascular hemolysis in the typical transfusion reaction scenario, making it the best answer.