Analysis of the expression of cloned HLA class I genes in mouse transfected L cells by quantitative flow cytometry

By using a calibrated cell sorter and monoclonal antibodies conjugated to fluorochromes, a quantitative analysis of the levels of expression of HLA class I molecules at the surface of cloned murine L cells transfected with purified A3, B7, or CW3 genes was performed and compared with radioimmunoassay data. We selected clones of heterogeneous levels of HLA class I expression, which were shown to remain constant over a period of 4 mo in absence of HAT selection and not to be correlated to the DNA copy number of the corresponding integrated gene.