Lewis A

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). There are two main types of Lewis antigens, Lewis a (Le-a) and Lewis b (Le-b). There are three common phenotypes: Le(a+b-), Le(a-b+), and Le(a-b-).

Lewis A Antigen