Which antibodies can be the cause of a severe delayed hemolytic transfusion reaction?

• A. Kidd (Jk)
• B. Duffy (Fy)
• C. MNS
• D. Rh

Answer: (A)

Delated hemolytic transfusion reactions occur when the patient has an alloantibody directed against donor red cell antigens, and the reaction can be especially severe when the antibody response upon re-exposure is rapid and robust. Kidd antibodies, anti-Jka or anti-Jkb, are classically associated with severe delayed reactions because they often produce a strong anamnestic response after the patient is re-exposed to the antigen. Even if the initial antibody level is low or undetectable, a subsequent transfusion can trigger a rapid rise in antibody, leading to brisk destruction of donor red cells days after the transfusion. This can result in significant hemolysis, hemoglobinemia, jaundice, and a positive DAT. Other antibodies like Duffy, MNS, or Rh can cause DHTR as well, but Kidd antibodies are particularly known for causing severe delayed reactions due to this pronounced memory response and the sometimes elusive detection on initial testing.