Here's a breakdown of their chemical nature:
* Glycoprotein: This means they are composed of two parts:
* Glycan: A carbohydrate chain attached to the protein backbone. It's the glycan portion that determines the ABO blood type.
* Protein: A polypeptide chain that acts as the backbone for the glycan.
* Glycan Structure: The specific sugars present in the glycan chain define the ABO blood type:
* Type A: N-acetylgalactosamine (GalNAc) is attached to the terminal position of the glycan chain.
* Type B: Galactose (Gal) is attached to the terminal position of the glycan chain.
* Type O: No terminal sugar is attached to the glycan chain.
* Genetically Determined: The ABO blood type is determined by the genes inherited from your parents. These genes code for specific enzymes that add the terminal sugar (GalNAc or Gal) to the glycan chain. Individuals with the "O" allele lack the enzyme required for adding the terminal sugar.
In summary: ABO isoantigens are glycoproteins whose differences lie in the specific sugars attached to their glycan chains. These differences are responsible for the distinct antigens recognized by the immune system, leading to the different ABO blood types.
