Transgenic mouse whose genome comprises: (a) a stably integrated human λ light chain locus, wherein said λ light chain locus is in the germline configuration and comprises the λ gene segments from 5 'of the gene from Vλ1-27 to 3 'of the λ enhancer in 3'； (b) a stably integrated part of a human κ light chain locus in the germline configuration, wherein said part comprises the Vκ genes starting at Vκ-B3 and ending at Vκ-OP11, with a deletion of Vκ -LP13 to Vκ -LP6； the Jκ region the Cκ region； the element of deletion of κ； and the 3 'and intronic enhancers of lgκ； (c) a stably integrated part of a human immunoglobulin heavy chain locus in the germline configuration, wherein said part comprises the VH genes starting at VH6-1 and ending at VH3-65: the DH region , the JH region, the genes of the Cμ constant region, the genes of the Cδ constant region, the genes of the Cγ constant region, the 3 'mouse enhancer and the human intronic enhancer, in which said region genes Cγ constant are selected from the group consisting of: genes from the human Cγ1 constant region, genes from the human Cγ2 constant region and genes from the human Cγ4 constant region； (d) homozygous inactivated endogenous immunoglobulin heavy chain loci； and (e) homozygous inactivated endogenous immunoglobulin κ light chain loci.Ratón transgénico cuyo genoma comprende: (a) un locus de cadena ligera λ humana integrado de manera estable, en el que dicho locus de cadena ligera λ está en la configuración de línea germinal y comprende los segmentos de gen de λ desde 5' del gen de Vλ1-27 hasta 3' del potenciador de λ en 3'； (b) una parte integrada de manera estable de un locus de cadena ligera κ humana en la configuración de línea germinal, en el que dicha parte comprende los genes de Vκ empezando en Vκ -B3 y terminando en Vκ - OP11, con una deleción de Vκ -LP13 a Vκ -LP6； la región Jκ la región Cκ ； el elemento de deleción de κ ； y los potenciadores en 3' e intrónico de lgκ ； (c) una parte integrada de manera es
