Antibody mimicking an anti-E antibody that binds to patient's E negative red cells

We have reported a rare case of auto anti-E antibody with specificity mimicking alloantibody with E specificity. A patient whose red cells typed as R1R1 and who had a positive direct antiglobulin test was admitted to our hospital. After standard serologic testing was performed, flow cytometry, Western blot analysis and differential allogenic adsorption test were used to verify whether antibody binds to the patient's red cells and normal red cells. A high titer anti-E antibody was detected transiently from the patient's serum and eluate. An indirect antiglobulin test using red cells treated by cysteine-activated papain and dithiothreitol (ZZAP) and chloroquine showed that both the patient's serum and eluate bound an apparent anti-E antibody to E negative patient's red cells. Fluorescence activated cells sorter (FACS) and Western blot analysis verified that the patient's red cells lacked E antigen. Further, it was clarified that the antibody does not bind to any E negative normal red cells by differential allogenic adsorption test. These results provide evidence that an antibody mimicking an E alloantibody can bind to patient's own E negative red cells but not to allogenic E negative red cells.