Abstract: The invention provides genetically modified non-human animals that express chimeric human/non-human T cell co-receptor polypeptides (e.g., CD4, CD8?, CD8?), as well as embryos, cells, and tissues comprising the same. Also provided are constructs for making said genetically modified animals and methods of making the same.

Abstract: The invention provides a genetically modified non-human animal that comprises in its genome unrearranged T cell receptor variable gene loci, as well as embryos, cells, and tissues comprising the same. Also provided are constructs for making said genetically modified non-human animal and methods of making the same. Various methods of using the genetically modified non-human animal are also provided.

Abstract: Non-human animals (and/or non-human cells) and methods of using and making the same are provided, which non-human animals (and/or non-human cells) have a genome comprising human antibody-encoding sequences (i.e., immunoglobulin genes). Non-human animals described herein express antibodies that contain human Ig? light chains, in whole or in part. In particular, non-human animals provided herein are, in some embodiments, characterized by expression of antibodies that contain human Ig? light chains, in whole or in part, that are encoded by human Ig? light chain-encoding sequences inserted into an endogenous Ig? light chain locus of said non-human animals. Methods for producing antibodies from non-human animals are also provided.

Abstract: The invention provides genetically modified non-human animals that express chimeric human/non-human MHC I polypeptide and/or human or humanized ?2 microglobulin polypeptide, as well as embryos, cells, and tissues comprising the same. Also provided are constructs for making said genetically modified animals and methods of making the same. Methods of using the genetically modified animals to study various aspects of the human immune system are provided.

Abstract: The invention provides genetically modified non-human animals that express chimeric human/non-human MHC I polypeptide and/or human or humanized ?2 microglobulin polypeptide, as well as embryos, cells, and tissues comprising the same. Also provided are constructs for making said genetically modified animals and methods of making the same. Methods of using the genetically modified animals to study various aspects of human immune system are provided.

Abstract: The invention provides genetically modified non-human animals that express chimeric human/non-human MHC I polypeptide and/or human or humanized ?2 microglobulin polypeptide, as well as embryos, cells, and tissues comprising the same. Also provided are constructs for making said genetically modified animals and methods of making the same. Methods of using the genetically modified animals to study various aspects of human immune system are provided.

Abstract: Non-human animals (and/or non-human cells) and methods of using and making the same are provided, which non-human animals (and/or non-human cells) have a genome comprising human antibody-encoding sequences (i.e., immunoglobulin genes). Non-human animals described herein express antibodies that contain human Ig? light chains, in whole or in part. In particular, non-human animals provided herein are, in some embodiments, characterized by expression of antibodies that contain human Ig? light chains, in whole or in part, that are encoded by human Ig? light chain-encoding sequences inserted into an endogenous Ig? light chain locus of said non-human animals. Methods for producing antibodies from non-human animals are also provided.

Abstract: The invention provides genetically modified non-human animals that express chimeric human/non-human T cell co-receptor polypeptides (e.g., CD4, CD8?, CD8?), as well as embryos, cells, and tissues comprising the same. Also provided are constructs for making said genetically modified animals and methods of making the same.

Abstract: The invention provides genetically modified non-human animals that express chimeric human/non-human MHC I polypeptide and/or human or humanized ?2 microglobulin polypeptide, as well as embryos, cells, and tissues comprising the same. Also provided are constructs for making said genetically modified animals and methods of making the same. Methods of using the genetically modified animals to study various aspects of human immune system are provided.

Abstract: Compositions and methods are provided for creating and promoting biallelic targeted modifications to genomes within cells and for producing non-human animals comprising the modified genomes. Also provided are compositions and methods for modifying a genome within a cell that is heterozygous for an allele to become homozygous for that allele. The methods make use of Cas proteins and two or more guide RNAs that target different locations within the same genomic target locus. Also provided are methods of identifying cells with modified genomes.

Abstract: Compositions and methods are provided for creating and promoting biallelic targeted modifications to genomes within cells and for producing non-human animals comprising the modified genomes. Also provided are compositions and methods for modifying a genome within a cell that is heterozygous for an allele to become homozygous for that allele. The methods make use of Cas proteins and two or more guide RNAs that target different locations within the same genomic target locus. Also provided are methods of identifying cells with modified genomes.

Abstract: Non-human animals and methods and compositions for making and using them are provided, which non-human animals have a genome comprising an engineered or recombinant diversity cluster within an immunoglobulin heavy chain variable region, which engineered or recombinant diversity cluster comprises an insertion of one or more DH segments that are each operably linked to a 23-mer recombination signal sequence. Methods for producing antibodies from non-human animals are also provided, which antibodies optionally contain human variable regions and rodent, e.g., constant regions.

Abstract: Compositions and methods are provided for creating and promoting biallelic targeted modifications to genomes within cells and for producing non-human animals comprising the modified genomes. Also provided are compositions and methods for modifying a genome within a cell that is heterozygous for an allele to become homozygous for that allele. The methods make use of Cas proteins and two or more guide RNAs that target different locations within the same genomic target locus. Also provided are methods of identifying cells with modified genomes.

Abstract: Provided herein are methods and compositions related to the in vivo testing of therapeutic agents comprising a human Fc in genetically modified rodents (e.g., the testing of the pharmacokinetic and/or pharmacodynamic properties of such a therapeutic agent in genetically modified rodents). In some embodiments the genetically modified rodents express antibodies comprising a human Fc (e.g., a human IgG1 Fc, a human IgG4 Fc). In some embodiments, the rodents express fully human antibodies (i.e., antibodies having human heavy chains and human light (? or ?) chains). In certain embodiments the genetically modified rodents comprise one or more Fc receptors with a human extracellular domain (e.g., a Neonatal Fc Receptor (FcRn), a ?-2-microglobulin polypeptide (?2M), a Fc ? receptor 1? (Fc?R1?), a Fc ? receptor 1 alpha (Fc?R1a), a Fc gamma receptor 2a (Fc?R2a), a Fc gamma receptor 2b (Fc?R2b), a Fc gamma receptor 3a (Fc?R3a), a Fc gamma receptor 3b (Fc?R3b), a Fc gamma receptor 2c (Fc?R2c)).

Abstract: The invention provides genetically modified non-human animals that express a humanized MHC II protein (humanized MHC II ? and ? polypeptides), as well as embryos, cells, and tissues comprising the same. Also provided are constructs for making said genetically modified animals and methods of making the same. Methods of using the genetically modified animals to study various aspects of human immune system are provided.

Abstract: The invention provides genetically modified non-human animals that express a humanized MHC II protein (humanized MHC II ? and ? polypeptides), as well as embryos, cells, and tissues comprising the same. Also provided are constructs for making said genetically modified animals and methods of making the same. Methods of using the genetically modified animals to study various aspects of human immune system are provided.

Abstract: The invention provides genetically modified non-human animals that express chimeric human/non-human MHC I and MHC II polypeptides and/or human or humanized ?2 microglobulin polypeptide, as well as embryos, cells, and tissues comprising the same. Also provided are constructs for making said genetically modified animals and methods of making the same. Methods of using the genetically modified animals to study various aspects of human immune system are provided.

Abstract: The invention provides genetically modified non-human animals that express chimeric human/non-human MHC I and MHC II polypeptides and/or human or humanized ?2 microglobulin polypeptide, as well as embryos, cells, and tissues comprising the same. Also provided are constructs for making said genetically modified animals and methods of making the same. Methods of using the genetically modified animals to study various aspects of human immune system are provided.

Abstract: The invention provides genetically modified non-human animals that express a humanized MHC II protein (humanized MHC II ? and ? polypeptides), as well as embryos, cells, and tissues comprising the humanized MHC II protein. Also provided are constructs for and methods of making said genetically modified non-human animals. Methods of using the genetically modified non-human animals to study various aspects of the human immune system are provided.

Abstract: The invention provides genetically modified non-human animals that express chimeric human/non-human MHC I and MHC II polypeptides and/or human or humanized ?2 microglobulin polypeptide, as well as embryos, cells, and tissues comprising the same. Also provided are constructs for making said genetically modified animals and methods of making the same. Methods of using the genetically modified animals to study various aspects of human immune system are provided.