Cells, vertebrates, populations and methods

1 . An isolated cell comprising a first antibody kappa light chain locus comprising in 5′ to 3′ direction:

(a) a light chain Eiκ intronic enhancer;

(b) a rearranged antibody variable region encoding a first rearranged antibody Vκ domain; and

(c) an antibody light chain constant region encoding a kappa light chain C domain;

wherein said kappa light chain locus is operable to express an antibody chain comprising in N- to C-terminal direction said rearranged antibody Vκ domain and said kappa light chain C domain, and wherein the isolated cell is not a human embryonic stem cell or a cell of a human embryo.

2 . The isolated cell of claim 1 , wherein said cell further comprises comprising an antibody heavy chain locus comprising in 5′ to 3′ direction

(a) a heavy chain intronic enhancer (Eμ);

(b) a rearranged antibody variable region encoding a rearranged antibody V domain;

(c) an optional switch sequence; and

(d) an antibody heavy chain constant region encoding a heavy chain CH1 domain;

wherein the first antibody heavy chain locus is operable to express an antibody chain comprising in N- to C-terminal direction said rearranged antibody V domain and said heavy chain CH1 domain, and wherein the isolated cell is not a human embryonic stem cell or human embryo.

3 . The isolated cell of claim 1 , wherein said first antibody kappa light chain locus comprises in 5′ to 3′ direction:

(a) a promoter operable for promoting transcription of said rearranged antibody variable region;

(b) a nucleotide sequence encoding a variable domain signal peptide;

(c) said intronic enhancer;

(d) said rearranged antibody variable region; and

(e) said antibody light chain constant region,

wherein the first antibody kappa light chain locus is operable to express RNA transcripts encoding in N- to C-terminal direction said variable domain signal peptide sequence fused to the amino acid sequence of said rearranged antibody variable domain.

4 . The cell of claim 1 , wherein the cell is an ES, iPS, hybridoma or B-cell.

5 . The cell of claim 1 , wherein the rearranged antibody variable region encodes a rearranged antibody Vκ domain that has a binding specificity for a first predetermined antigen or a first epitope when paired with another rearranged Vκ domain, wherein said first antibody kappa light chain locus is operable to express an antibody chain that comprises a rearranged antibody Vκ domain that retains said binding specificity for said first predetermined antigen or said first epitope when paired with said another rearranged V domain.

6 . The cell of claim 1 , wherein the cell comprises a second antibody locus that is operable to express a second antibody chain, wherein the second chain comprises a second rearranged antibody V domain that forms a binding site with said first rearranged antibody Vκ domain, wherein the binding site is capable of specifically binding to a predetermined antigen or epitope.

7 . The cell of claim 5 , wherein the cell comprises a second antibody locus that is operable to express a second antibody chain, wherein the second chain comprises a second rearranged antibody V domain that forms a binding site with the first rearranged antibody V domain, wherein the binding site is capable of specifically binding to a predetermined antigen or epitope, wherein the predetermined antigens are different and said other and second rearranged antibody V domains are different; or wherein the epitopes are different and said other and second rearranged antibody V domains are different.

8 . The cell of claim 7 , wherein said second rearranged antibody V domain is a VH domain.

9 . The cell of claim 1 , wherein the variable region is within 0.5 kb 3′ of the enhancer.

10 . The cell of claim 1 , wherein the locus comprises a second enhancer that is 3′ of the constant region.

11 . The cell of claim 1 , wherein the cell is a non-human mammal, mouse, rat or rodent cell.

12 . The cell of claim 1 , wherein said constant region is at an endogenous antibody locus of the cell.

13 . The cell of claim 12 wherein said endogenous locus is an endogenous kappa chain locus.

14 . The cell of claim 1 , wherein the cell is homozygous for said locus.

15 . The cell of claim 1 , wherein the cell genome comprises a second antibody locus, wherein the second locus is an unrearranged antibody heavy chain locus comprising in 5′ to 3′ direction:

(a) one or more VH gene segments;

(b) one or more DH gene segments;

(c) one or more JH gene segments; and

(d) a heavy chain constant region encoding one or more CH domains;

wherein the heavy chain locus is operable to express a plurality of heavy chains, optionally comprising a plurality of antigen specificities or affinities, each said heavy chain being capable of pairing with an antibody chain encoded by the first locus to produce paired chains that comprise an antigen binding site.

16 . The cell of claim 1 , wherein

(a) the cell is a mouse cell, said variable region is a human kappa variable region, the intronic enhancer is a mouse intronic enhancer at an endogenous kappa antibody locus of the cell and said constant region is a mouse, rat or human constant region; or

(b) the cell is a rat cell, said variable region is a human kappa variable region, the intronic enhancer is a rat intronic enhancer at an endogenous kappa antibody locus of the cell and said constant region is a mouse, rat or human constant region.

17 . The cell of claim 1 , wherein the rearranged variable region comprises:

(a) human IGκ1-39 and IGκJ1 or IGκ5 and optionally operably connected to human germline IGKV1-39 promoter and/or signal peptide-encoding nucleotide sequence; or

(b) human IGK3-20 and IGKJ1 or IGKJ5 and optionally operably connected to human germline IGKV3-20 promoter and/or signal peptide-encoding nucleotide sequence.

18 . An isolated population of nonhuman mammalian cells comprising a plurality of spleen cells, bone marrow cells, B-cells or blood cells, wherein each cell in said population of cells comprises a first antibody kappa light chain locus, wherein the locus comprises in 5′ to 3′ direction:

(a) a light chain Eiκ intronic enhancer;

(b) a rearranged antibody variable region encoding a first rearranged antibody Vκ domain; and

(c) an antibody light chain constant region encoding a kappa light chain C domain; wherein said kappa light chain locus is operable to express an antibody chain comprising in N- to C-terminal direction said rearranged antibody Vκ domain and said kappa light chain C domain.

19 . An isolated population of hybridoma cells, CHO cells, HEK cells, MEF cells, COS cells, or HeLa cells, wherein each cell in said population of cells comprises a first antibody kappa light chain locus, wherein the locus comprises in 5′ to 3′ direction:

(a) a light chain Eiκ intronic enhancer;

(b) a rearranged antibody variable region encoding a first rearranged antibody Vκ domain; and

(c) an antibody light chain constant region encoding a kappa light chain C domain; wherein said kappa light chain locus is operable to express an antibody chain comprising in N- to C-terminal direction said rearranged antibody Vκ domain and said kappa light chain C domain, wherein the population of cells expresses at least 10 different antibody species, wherein

(i) at least 95% of the antibodies share the same kappa light chain VL domain and the population comprises at least 10 different VH domain species; or

(ii) the antibodies comprise kappa light chain VL domains derived from the recombination of a first Vκ gene segment and a first Jκ gene segment, wherein at least 95% of all said kappa light chain VL domains derived from said recombination comprise the same VL amino acid sequence and the population comprises at least 10 different VH domain species.