Expression of HLA-DR antigen in human class II mutant B-cell lines by double infection with retrovirus vectors

A new retrovirus vector containing the gene for hygromycin B resistance (hyg) as a selectable marker under the control of an internal simian virus 40 promoter was constructed. It was used, together with an analogous previously described vector, DO1, which contains the gene for G418 resistance, to introduce and express the genes for the two chains of a human class II major histocompatibility complex antigen in NIH 3T3 cells. In addition, these vectors were used to express DR antigens in two human mutant B-lymphoblastoid cell lines, one of which was deleted for both alleles of the DR alpha gene and the other of which expressed no class II antigens because of a genetic defect in a putative trans-acting regulatory factor.