Expression of functional mouse antibodies directed against the tumour marker human placental alkaline phosphatase in non-lymphoid cells.

A mouse hybridoma cell line was isolated which produces monoclonal antibodies (MAbs) of the IgG2b, kappa subtype directed against the tumour-associated marker human placental alkaline phosphatase (hPLAP). The mRNAs coding for the heavy (H) and light (L) chains were cloned as cDNA copies. These genes were then separately inserted into the eukaryotic expression vector pSV23p, under control of the SV40 early promoter. Both genes were introduced with the DEAE-dextran technique in COSI cells, and 72 hr after transfection, 10 ng/ml functional antibodies could be detected in the supernatant of the cells. Permanent CHO cell lines secreting 100 ng/ml functional antibodies were established upon transfection of CHO (dhfr-) cells with the plasmids containing the H and L cDNAs and the plasmid pAdD26SVp-(A)-3 carrying the mouse dihydrofolate reductase (dhfr) gene. A plasmid construction in which we inserted a stop codon-containing sequence behind the hinge region of the H-chain cDNA sequence yielded immuno-competent F(ab')2 molecules upon transfection of COS or CHO cells. Our results indicate that not only lymphoid cells, but also non-lymphoid cells, are capable of synthesis and assembly of immunoglobulin chains that are immunologically fully competent.