FINAL DIAGNOSIS: LEWIS A ANTIBODY The Lewis system antigens are
uncommonly clinically significant; however, they are of great
interest in immunohematology in that they are the only red cell
antigens which are not produced by the RBC itself. The Lewis
antigens originate in the body secretions, and are subsequently
adsorbed onto the surface of the red cell. It has also been
noted that the Le substance can dissociate from the cells just
as readily; therefore, Lewis-positive donor cells can become
Lewis-negative following transfusion into an individual with a
Lewis-negative phenotype.1 The Lewis antigen is created within
many different cells in the body (usually the same which produce
ABH antigens) and secreted as a water-soluble product. The Lewis
and ABH antigens share the same precursor substance, the type 1
oligosaccharide chain. The Lewis (Le) gene is located on
chromosome 19 and codes for a fucosyl-transferase that attaches
a fucose to the N-acetyl-glucosamine of this precursor
substance.2 The secretor gene