Which antigen is destroyed by enzymes?

• A. Fy^a
• B. Duffy
• C. Jk^a
• D. I antigen

Answer: (A)

Enzymes used to treat red cells can alter or remove some surface antigens, changing whether an antibody will bind. The Fy^a antigen in the Duffy blood-group system is a classic example of an antigen that is destroyed by proteolytic enzymes such as ficin or papain. When red cells are enzyme-treated, Fy^a antigens are essentially removed from the cell surface, so anti-Fya no longer reacts with those cells. This makes Fy^a the best answer for an antigen that is destroyed by enzymes.

Jk^a and I antigens are not consistently destroyed by standard enzyme treatment, and while the Duffy system includes Fy^a and Fy^b, the specific, best-known example among the options is Fy^a.