Which antigen is associated with the Lewis blood group system?

Which antigen is associated with the Lewis blood group system?

• A. Lea
• B. P
• C. M
• D. N

Answer: (A)

Lea is the Lewis system antigen. The Lewis blood group is built around two main antigens, Le^a and Le^b, whose expression depends on fucosyltransferase enzymes that act on a type 1 precursor. Le^a is produced when only the FUT3 enzyme is active, while Le^b requires both FUT2 (secretor) and FUT3 activity, with expression differing in secretors versus nonsecretors. In practical terms, Lea is the hallmark antigen of the Lewis system because it represents one of the two standard Lewis antigens tested for. The other options come from different blood group systems (M and N from the MNS system, P from the P system) and are not Lewis antigens.

Lea is the Lewis system antigen. The Lewis blood group is built around two main antigens, Le^a and Le^b, whose expression depends on fucosyltransferase enzymes that act on a type 1 precursor. Le^a is produced when only the FUT3 enzyme is active, while Le^b requires both FUT2 (secretor) and FUT3 activity, with expression differing in secretors versus nonsecretors. In practical terms, Lea is the hallmark antigen of the Lewis system because it represents one of the two standard Lewis antigens tested for. The other options come from different blood group systems (M and N from the MNS system, P from the P system) and are not Lewis antigens.