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.

Epitopes of HLA-A, B, C, DR, DQ, DP and MICA antigens.

This chapter presents lists of HLA epitopes that have been defined to date. It also presents examples of reactions of mAb and eluted allosera with the class I, class II and MICAsingle antigen beads. To date, we have identified 110 class I epitopes, of which 47 were defined by mAbs and 63 by alloantibodies that were eluted from rHLA class I single antigen cell lines. We listed 34 epitopes shared by the HLA-A locus antigens, 44 epitopes shared by HLA-B locus antigens, 4 epitopes shared by HLA-C locus antigens, 20 inter-locus epitopes shared by HLA-A-B locus antigens, 5 inter-locus epitopes shared by HLA-B-C locus antigens and 3 inter-locus epitopes shared by HLA-A-B-C locus antigens. Sixty HLA-DR epitopes have been defined mostly by one amino acid (aa) residue on the HLA-DR beta chain. Eighteen HLA-DQ epitopes have been defined on the HLA-DQB chain and on the HLA-DQA chain of the HLA-DQ antigens. A few DQ epitopes were defined by one aa residue. However, most can be defined by several alternative combinations of aa residues. DQA and DP epitopes--few in number at this time--were identified. Only seven MICA epitopes have been defined to date. All epitopes can be defined by an exclusive amino acid.