Appendix 06. The immuno-dominant sugars of the A and B antigens are GalNAc (N-acetyl-D-galactosamine) and galactose, respectively.

 

The chemical structures of these sugars are shown. The only difference between these two sugars is the N-acetyl group (-NHCOCH3) and the hydroxyl group (-OH), which are attached at the 2nd position of the carbon ring in GalNAc and galactose, respectively.