What is typically weakly expressed or not expressed at all on cord blood cells?

Lewis antigens are typically weakly expressed or not expressed at all on cord blood cells. This is due to the developmental stage of neonates, as the Lewis blood group system is not fully developed at birth. Lewis blood group antigens are also known to be dependent on the presence of certain genes that may not be fully active in fetal development, leading to minimal or absent expression in newborns.

In contrast, ABO antigens are well expressed and can be identified in cord blood. Rh antigens are also present on cord blood cells and are crucial for determining potential Rh incompatibility in newborns. HLA antigens, which play a key role in immune response and tissue compatibility, are expressed on all nucleated cells, including those in cord blood. Therefore, the weak expression of Lewis antigens on cord blood is a recognized characteristic of neonatal blood.