Genetically modified mice are provided that express human » variable (hV») sequences. The mice provided include a mouse comprising: (a) an endogenous heavy chain allele comprising an unrearranged human V H , an unrearranged human D H and an unrearranged human J H gene segment； and (b) an endogenous » (lambda) light chain allele comprising an unrearranged human V» and an unrearranged human J» gene segment. The mice provided include mice that express hV» sequences from an endogenous mouse » light chain locus, mice that express hV» sequences from an endogenous mouse º light chain locus, and mice that express hV» sequences from a transgene or an episome wherein the hV» sequence is linked to a mouse constant sequence. Mice are provided that are a source of somatically mutated human » variable sequences useful for making antigen-binding proteins. Compositions and methods for making antigen-binding proteins that comprise human » variable sequences, including human antibodies, are provided.ヒトλ可変（ｈＶλ）配列を発現する遺伝的に改変されたマウス（内在性マウスλ軽鎖遺伝子座からｈＶλ配列を発現するマウス、内在性マウスκ軽鎖遺伝子座からｈＶλ配列を発現するマウス、および導入遺伝子またはエピソームからｈＶλ配列を発現するマウスを含む）が提供され、ここで、そのｈＶλ配列は、マウス定常配列に接続されている。抗原結合タンパク質の作製に有用な体細胞変異したヒトλ可変配列の起源となるマウスが提供される。ヒト抗体を含むヒトλ可変配列を含む抗原結合タンパク質を作製するための組成物および方法が提供される。
