Role of antigen density in immune lysis of interferon-treated human lymphoid cells: analysis with monoclonal antibodies to the HLA-A,B antigenic molecular complex and to Ia-like antigens.

Cultured human lymphoid WI-L2 cells incubated with human leucocyte interferon (final concentration 500 and 2000 U/ml) for 16 h at 37 degrees C acquire increased susceptibility to complement and cell-dependent lysis mediated by monoclonal antibodies to HLA-A,B antigens and to human beta 2-microglobulin but do not change in their susceptibility to immune lysis mediated by monoclonal antibodies to human Ia-like antigens. Changes in susceptibility to immune lysis of interferon-treated lymphoid cells are likely to reflect changes in antigen density, since binding assays with monoclonal antibodies and quantitative absorption assays with alloantisera have shown that the expression of HLA-A,B antigens and beta 2-microglobulin is significantly increased on interferon-treated lymphoid cells, whereas that of Ia-like antigens in not changed.