ABO Blood-Group System

**Definition:** The major human blood type system which depends on the presence or absence of two antigens A and B. Type O occurs when neither A nor B is present and AB when both are present. A and B are genetic factors that determine the presence of enzymes for the synthesis of certain glycoproteins mainly in the red cell membrane.

**Tree numbers:** - D23.050.301.290.031 - D23.050.705.230.031

**Synonyms:** - ABH Blood Group - H Blood Group - H Blood Group System - ABO Blood Group