"Such suppression of blood group antigens, with associated antibody production against the suppressed antigen, is an established phenomenon, seen for example in Kell, Kidd and LW systems.

After 50 years since its first detection, researchers have discovered the genetic background of the AnWj blood group antigen. Although rare, AnWj-negative phenotypes can have transfusion reactions ...

About 80 percent of people secrete blood group antigens in other bodily fluids, such as saliva, mucus, and sweat. This group of people is referred to as secretors.