FOUR EPITOPES ON THE RH ANTIGEN E RECOGNIZED BY HUMAN MONOCLONAL ANTIBODIES

E antigen of the human Rh blood group system was serologically analyzed with five human monoclonal anti-E antibodies including a newly developed HMR37 antibody. Four different reaction patterns of these monoclonal antibodies were observed by agglutination test and fluorescence flowcytometry with six Evariant cells showing incompatible reaction between monoclonal anti-E and conventional polyclonal anti-E. The mutual inhibition study using fluorescence-labelled antibodies also supported that four epitopes recognized by the monoclonal antibodies are on the normal EE cells. These results indicate that at least four distinct epitopes are present on the E antigen, and suggest that anti-E antibody production may occur in E-positive individuals partially lacking the E epitope(s).