What is the term for the phenomenon where an individual's red blood cells have a weakened or absent expression of the A or B antigen, resulting in a decreased reactivity with anti-A or anti-B antibodies?

A Subgrouping
B Weak antigen expression ✓
C Bombay phenotype
D Genetic variation

Explanation

Weak antigen expression refers to the decreased reactivity of red blood cells with anti-A or anti-B antibodies due to a weakened or absent expression of the A or B antigen.

Source

American Association of Blood Banks (AABB) guidelines
Hematology Hematology: Blood Grouping and Crossmatching Hematology: Blood Grouping and Crossmatching Medium MEDICAL Confidence: high