This gene encodes the Landsteiner-Wiener (LW) blood group antigen(s) that belongs to the immunoglobulin (Ig) superfamily, and that shares similarity with the intercellular adhesion molecule (ICAM) protein family. This ICAM protein contains 2 Ig-like C2-type domains and binds to the leukocyte adhesion LFA-1 protein. The molecular basis of the LW(A)/LW(B) blood group antigens is a single aa variation at position 100; Gln-100=LW(A) and Arg-100=LW(B). Alternative splicing results in multiple transcript variants encoding distinct isoforms.