Altered structure of HLA class I heavy chains associated with mouse beta-2 microglobulin

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Abstract
The serological reactivities of HLA-A3, -B7, and -CW3 heavy chains associated with either mouse, bovine, or human beta-2 microglobulin (β2m) and expressed on the surface of transfected mouse fibroblasts were analyzed. All reactivities associated with one cluster (defined by monoclonal antibody W6/32) of antigenic determinants expressed by these HLA class I molecules were lost, or profoundly reduced, after each heavy chain associated with mouse β2-m. Expression by the transfected fibroblasts of the HLA-A3, -B7, and -CW3 heavy chains in association with human β2m restores these reactivities. Since most of the amino acid differences between mouse and human β2m probably correspond to externally oriented hydrophilic residues, these results suggest that critical interactions in the three-dimensional structure of HLA class I molecules occur between the light chain and the first two external domains of the class I heavy chains, to which some of the altered reactivities have been mapped.