We have created mouse-human antibody molecules of defined antigen-binding specificity by taking the variable region genes of a mouse antibody-producing myeloma cell line with known antigen-binding specificity and joining them to human immunoglobulin constant region genes using recombinant DNA techniques. Chimeric genes were constructed that utilized the rearranged and expressed antigen-binding variable region exons from the myeloma cell line S107, which produces an IgA (K) anti-phosphocholine antibody. The heavy chain variable region exon was joined to human IgG1 or IgG2 heavy chain constant region genes, and the light chain variable region exon from the same myeloma was joined to the human ic light chain gene. These genes were transfected into mouse myeloma cell lines, generating transformed cells that produce chimeric mouse-human IgG (K) or IgG (K) anti-phosphocholine antibodies. The transformed cell lines remained tumorigenic in mice and the chimeric molecules were present in the ascitic fluids and sera of tumor-bearing mice.The capability to transfer immunoglobulin genes into lymphoid cells where they produce protein in quantities sufficient for structural studies (1-3) provides us with the opportunity to generate and characterize novel immunoglobulin molecules. Cloned variable (V) region genes from mouse or rat hybridoma cell lines can be ligated to human constant (C) region genes and we would expect that these chimeric genes can be transfected into mouse myeloma cells, which then will produce novel human antibody molecules. We would thus produce antibodies that are largely human but which have antigen-binding specificities generated in mice. The additional potential for in vitro manipulation and alteration of both the antigen-binding site and the structures correlated with biological effector functions of these antibody molecules using recombinant DNA techniques would introduce a powerful approach for further understanding antibody structure, function, and immunogenetics.As we show here, both chimeric mouse heavy chain V region exon (VH)-human heavy chain C region genes and chimeric mouse light chain V region exon (VK)-human K light chain gene constructs are expressed when transfected into mouse myeloma cell lines. When both chimeric heavy and light chain genes are transfected into the same myeloma cell, an intact tetrameric (H2L2) chimeric antibody is produced.In this study we used VH and VK exons from the mouse phosphocholine (PCho)-binding antibody-producing S107 myeloma cell line (4, 5). Chimeric mouse-human anti-PCho antibodies were produced in culture by appropriate transfected cell lines or by "transfectomas" obtained when such cell lines are injected into mice.

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A simple method is described for the generation of a biologically produced mouse/human chimeric hetero-bifunctional antibody that has dual specificity for human carcinoembryonic Ag and metal chelate haptens. Two large compound chimeric vectors each containing the genetic information to produce a single antibody specificity were sequentially electroporated into the murine nonsecreting hybridoma SP2/0. This led to the isolation of a clone expressing high levels of total IgG (up to 25 micrograms/ml/10(6) cells), 10 to 20% of which showed simultaneous reactivity with both Ag. Binding studies showed that the immunoreactivities and affinity constants for the individual arms of the bifunctional antibody were equivalent to those seen with the parental antibodies.

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