HLA antigen structural gene mutants selected with an allospecific monoclonal antibody.

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Abstract
The HLA-A2 antigen-specific monoclonal antibody BB7.2 and complement were used to immunoselect mutants from an ethyl methanesulfonate-mutagenized human B lymphoid cell line, T5-1. Surviving colonies were screened by radioimmune binding with BB7.2 and with a monospecific HLA-A2 alloantiserum, Stewart, and HLA antigens of selected clones were immunoprecipitated and studied by isoelectric focusing. Several classes of mutants could be distinguished: mutants that expressed no HLA-A2 H chain; mutants that expressed an HLA-A2 H chain that was unable to associate with .beta.2-microglobulin (.beta.2m) and was not expressed at the cell surface; mutants with reduced HLA-A2 H chain-.beta.2m association and cell surface expression of HLA-A2 dimer with or without heavy chain charge alterations; mutants with normal HLA-A2 H chain-.beta.2m association and normal quantitative cell surface HLA-A2 expression but with HLA-A2 H chain charge alterations; and mutants with as yet incompletely defined lesions. Mutants with altered cell surface HLA antigens were not found in previous selections with alloantisera and should be useful for epitope mapping and structure-function studies of HLA molecules.