ABO antigens are not seen in aEUR’
**Core Concept**
ABO antigens are carbohydrate molecules present on the surface of red blood cells, functioning as a vital component of the immune system to prevent transfusion reactions. The ABO blood group system is the most important blood group system in transfusion medicine.
**Why the Correct Answer is Right**
The ABO antigens are not expressed on the red blood cells of individuals with the Bombay phenotype (Oh blood group). This is due to a mutation in the FUT1 gene, which encodes for the enzyme fucosyltransferase 1 responsible for adding fucose sugar molecules to the ABO antigens. As a result, individuals with the Oh blood group lack ABO antigens on their red blood cells. This condition makes them universal non-donors, as they cannot donate blood to anyone.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as ABO antigens are indeed expressed on the red blood cells of individuals with the A and B blood groups.
**Option B:** This option is incorrect as ABO antigens are not typically seen on the red blood cells of individuals with the AB blood group, which expresses both A and B antigens.
**Option C:** This option is incorrect as ABO antigens are indeed expressed on the red blood cells of individuals with the O blood group, which expresses neither A nor B antigens.
**Clinical Pearl / High-Yield Fact**
The Bombay phenotype (Oh blood group) is a rare condition characterized by the absence of ABO antigens on the red blood cells, making it a significant consideration in blood transfusion medicine.
**Correct Answer: D. Individuals with the Oh blood group.**