Further Characterization of Erythrocyte p 80 and the Membrane Protein Defect

We have previously shown that the In(Lu) gene downregulates expression of an erythrocyte protein antigen identified by murine monoclonal antibody (MoAb) A3D8. In the present study we have examined In(Lu) Lu(a b -) erythrocytes for expression of additional epitopes on the erythrocyte 80 kilodalton protein (p80) bearing the A3D8 antigen. Using a total of seven additional MoAbs that recognize three epitopes on erythrocyte p80. we have shown that In(Lu) Lu(a b ) erythrocytes exhibit downregulation of expression of all three epitopes. In(Lu) erythrocytes also showed a reduction in their reactivity to rabbit antibodies produced against purified p80 from either erythrocytes or lymphocytes. Furthermore the reactivity of the MoAbs was not altered by treatment of the cells with neuraminidase but was substantially reduced by treatment of cells with trypsin or chymotrypsin. The polyclonal antip80 sera were shown to react with a fragment of 50.000