Adsorption of Lec and Led from plasma onto red blood cells

When red blood cells lacking a particular antigen (Lea, Leb, Lec or Led) were incubated with plasma from a donor whose red blood cells had that antigen, the red blood cells became agglutinable by the antiserum that agglutinated the red blood cells of the plasma donor. The presence of each of these antigens on an individual's red blood cells correlates with the presence of a soluble antigen in his plasma, presumably glycosphingolipid, which is capable of adsorbing onto red blood cells.