Lewis X

Lewis X is one of members of the Lewis antigen system. The Lewis antigen system is a human blood group system. It is based upon two genes on chromosome 19: FUT3, or Lewis gene; and FUT2, or Secretor gene. Both genes are expressed in glandular epithelia. FUT2 has a dominant allele which codes for an enzyme (designated Se) and a recessive allele which does not produce a functional enzyme (designated se). Similarly, FUT3 has a functional dominant allele (Le) and a non-functional recessive allele (le). The Le(b) and H antigens are receptors for the bacteria Helicobacter pylori, a gram-negative bacterium that can cause gastritis and has been implicated in peptic ulcer disease, gastric adenocarcinoma, mucosa-associated lymphoma (or mucosal associated lymphatic tissue lymphoma – MALToma) and idiopathic thrombocytopenic purpura (ITP).

Lewis X