N-acetyllactosamine, the base unit in I and i antigens The<unk>  is a human blood group system based upon a gene on chromosome 6 and consisting of the I antigen and the i antigen. The I antigen is normally present on the cell membrane of red blood cells in all adults, while the i antigen is present in fetuses and newborns.
Ii antigen system
MNS antigen system
Yt antigen system
Kidd antigen system
Lewis antigen system
Duffy antigen system
Lutheran antigen system
Kell antigen system