Other than the D antigen, what other blood group antigen is potent?

• A. K
• B. P
• C. M
• D. N

Answer: (A)

Potency here means how strongly an antigen can provoke an alloimmune antibody response when an antigen-negative person is exposed. D is the most potent, and among the remaining antigens listed, the K antigen in the Kell system is known to be highly immunogenic. When someone lacking K is exposed to K-positive blood, anti-K antibodies are commonly formed and can cause clinically significant problems, including hemolytic transfusion reactions and hemolytic disease of the fetus and newborn.

The M and N antigens of the MNS system tend to be less immunogenic, and antibodies to them are often less clinically significant. Anti-P1 antibodies are also usually benign or clinically mild. Therefore, K stands out as the most potent among the options after D.