Immortalization of plasma cells by plasmid DNA and its hybridoma

Human plasma cell lines producing IgG were cloned by the limiting dilution method from polyclonally immortalized B-cell lines with the plasmid DNA (pSVTLbsr) containing simian virus 40 (SV40)-gene from primary peripheral blood mononuclear cells of healthy and nonimmune volunteers. The plasma cell lines fused well with conventional partner cells and became evenly IgG-producing hybridomas at high efficiency, especially with the partner cell from human origin. One of the difficulties in obtaining stable IgG-producing hybridoma using Epstein-Barr virus (EBV) transformation followed by back fusion with partner cells, might mainly be attributed to the inability to immortalize plasma cells on account of the very low density of CD21 (EBV receptor) on the cell surface. The present CD21-independent immortalization by plasmid DNA and by the infection with SV40 protein-coated plasmid DNA will be a potentially effective method to obtain IgG-producing human monoclonal antibodies.