New HLA class I epitopes defined by murine monoclonal antibodies

This study defines 10 epitopes by murine monoclonal antibodies, of which seven are new and three were previously defined by alloantibodies. Of particular interest, three antibodies reacted with almost all Bw4-associated antigens except that each was negative with one or two of the antigens. One was negative with B13, one negative with A25, and another negative with B13 & A24 antigens. These monoclonal antibodies exhibited reactivity contrary to Bw4 allosera, which typically react with all Bw4-associated antigens. All monoclonal antibodies were tested with a panel of 97 human leukocyte antigen (HLA) class I (A, B, and Clocus) rHLA single antigens (SA) individually coupled to different microsphere beads. Identifying HLA antigens sharing distinct epitopes can be helpful when selecting patient–donor transplantation pairs, explaining antibodies against rare specificities, or against non–donor-specific antigens (NDSA). This study adds seven new HLA class I epitopes to 103 already defined epitopes and provides more evidence that a monoclonal antibody and alloantibody can target the same epitope. The fact that mAbs can target the same epitopes targeted by allosera, makes mAbs useful in studies of cross-reactivity in HLA.