A strong antibody reacting with enzyme modified E positive red blood cells

A high titer antibody was discovered in a healthy young man of blood group A1 R2r. The antibody strongly agglutinated all E positive red blood cells including his own, which had been modified by papain, ficin and bromelin, but only very weakly when modified by trypsin. The antibody was shown to be an IgM antibody. It did not react with unmodified red blood cells.