Antibody producing non-human animals

1. A method for producing a library of cells, wherein essentially each cell comprises nucleic acid that encode at least two different heavy chain variable regions each having specificity for different targets or for different target epitopes, the method comprising:

isolating nucleic acid encoding heavy chain variable regions from B cells of transgenic murine animals that have been immunized to generate an immune response against different targets or targets containing different target epitopes,

wherein the genomes of the transgenic murine animals comprise a transgene comprising a single human immunoglobulin light chain V gene segment fused to a single human immunoglobulin light chain J gene segment, wherein the fused V/J gene segments encode a rearranged immunoglobulin light chain variable region, wherein the transgene lacks a regulatory element that contributes to somatic hypermutation of the rearranged immunoglobulin light chain variable region, and wherein the transgene comprises a light chain constant region gene segment;

wherein at least one of the endogenous light chain loci in said transgenic murine animals is functionally silenced; and

wherein said transgenic murine animals produce populations of B cells producing repertoires of target- or target epitope-specific antibodies, wherein said repertoires of antibodies comprise the rearranged light chain immunoglobulin variable region encoded by the fused V/J gene segments paired with a diversity of heavy chain variable regions; and

transfecting nucleic acid encoding said heavy chain variable regions and nucleic acid encoding said rearranged immunoglobulin light chain variable region into host cells, and allowing for integrating of said nucleic acid into the genome of said host cells, thereby producing a library of cells that produces antibodies comprising said heavy chain variable regions and said rearranged light chain variable region.

2. The method of claim 1 , wherein said transgenic murine animals are transgenic mice.

3. The method of claim 1 , wherein said transfected cells are subjected to a cloning step.

4. The method of claim 1 , wherein each of said nucleic acid encoding said at least two different heavy chain variable regions are under control of different regulatory elements.

5. The method of claim 4 , wherein said different regulatory elements give rise to different expression levels of said at least two different heavy chain variable regions.

6. The method of claim 1 , wherein the host cells are immortalized host cells.

7. The method of claim 1 , wherein said nucleic acid comprises nucleic acid encoding a secretion signal.

8. The method of claim 1 , wherein the transgene comprises a murine light chain constant region gene segment.

9. The method of claim 1 , wherein the transgene comprises a human light chain constant region gene segment.

10. The method of claim 1 , wherein essentially each cell comprises nucleic acid that encodes two different heavy chain variable regions each having specificity for different targets or for different target epitopes.

11. A method for producing a library of cells, wherein essentially each cell comprises nucleic acid that encode at least two different heavy chain variable regions each having specificity for different targets or for different target epitopes, the method comprising:

isolating nucleic acid encoding heavy chain variable regions from B cells of transgenic mice that have been immunized to generate an immune response against different targets or targets containing different target epitopes,

wherein the genomes of the transgenic mice comprise a transgene comprising a single human immunoglobulin light chain V gene segment fused to a single human immunoglobulin light chain J gene segment, wherein the fused V/J gene segments encode a rearranged immunoglobulin light chain variable region, wherein the transgene lacks a regulatory element that contributes to somatic hypermutation of the rearranged immunoglobulin light chain variable region, and wherein the transgene is linked to an endogenous light chain constant region gene segment;

wherein at least one of the endogenous light chain loci in said transgenic mice is functionally silenced; and

wherein said transgenic mice produce populations of B cells producing repertoires of target- or target epitope-specific antibodies, wherein said repertoires of antibodies comprise the rearranged light chain immunoglobulin variable region encoded by the fused V/J gene segments paired with a diversity of heavy chain variable regions; and

transfecting nucleic acid encoding said heavy chain variable regions and nucleic acid encoding said rearranged immunoglobulin light chain variable region into host cells, and allowing for integrating of said nucleic acid into the genome of said host cells, thereby producing a library of cells that produces antibodies comprising said heavy chain variable regions and said rearranged light chain variable region.

12. The method of claim 11 , wherein said transfected cells are subjected to a cloning step.

13. The method of claim 11 , wherein each of said nucleic acid encoding said at least two different heavy chain variable regions are under control of different regulatory elements.

14. The method of claim 13 , wherein said different regulatory elements give rise to different expression levels of said at least two different heavy chain variable regions.

15. The method of claim 11 , wherein the host cells are immortalized host cells.

16. The method of claim 11 , wherein said nucleic acid comprise nucleic acid sequences encoding a secretion signal.

17. The method of claim 11 , wherein essentially each cell comprises nucleic acid that encodes two different heavy chain variable regions each having specificity for different targets or for different target epitopes.