Abstract: Switch regions derived from an immunoglobulin (Ig) gene are used to direct recombination between a targeting construct containing a promoter, a switch region (S1), and 2) a target locus minimally containing a promoter, a switch region (S2), and a target sequence.

Abstract: In accordance with the present invention, there are provided fully human monoclonal antibodies against human epidermal growth factor receptor (EGF-r). Nucelotide sequences encoding and amino acid sequences comprising heavy and light chain immunoglobulin molecules, particularly sequences corresponding to contiguous heavy and light chain sequences from CDR1 through CDR3, are provided. Hybridomas expressing such immunoglobulin molecules and monoclonal antibodies are also provided.

Abstract: The present invention features a method of producing a multimeric protein from a hybrid cell formed from the fusion of two or more cells, each of which cell is engineered to express one component of the multimeric protein, as well as a method for screening for successful fusion of the cells to produce a desired hybrid cell. The methods of the invention are widely applicable to the production of proteins having two or more components.

Abstract: The subject invention provides non-human mammalian hosts characterized by inactivated endogenous Ig loci and functional human Ig loci for response to an immunogen to produce human antibodies or analogs thereof. The hosts are produced by multiple genetic modifications of embryonic cells in conjunction with breeding. Different strategies are employed for recombination of the human loci randomly or at analogous host loci. Chimeric and transgenic mammals, particularly mice, are provided, having stably integrated large, xenogeneic DNA segments. The segments are introduced by fusion with yeast spheroplasts comprising yeast artificial chromosomes (YACs) which include the xenogeneic DNA segments and a selective marker such as HPRT, and embryonic stem cells.

Abstract: Fully human antibodies against a specific antigen can be prepared by administering the antigen to a transgenic animal which has been modified to produce such antibodies in response to antigenic challenge, but whose endogenous loci have been disabled. Various subsequent manipulations can be performed to obtain either antibodies per se or analogs thereof.

Abstract: A method to produce a cell expressing an antibody from a genomic sequence of the cell comprising a modified immunoglobulin locus using Cre-mediated site-specific recombination is disclosed. The method involves first transfecting an antibody-producing cell with a homology-targeting vector comprising a lox site and a targeting sequence homologous to a first DNA sequence adjacent to the region of the immunoglobulin loci of the genomic sequence which is to be converted to a modified region, so the first lox site is inserted into the genomic sequence via site-specific homologous recombination. Then the cell is transfected with a lox-targeting vector comprising a second lox site suitable for Cre-mediated recombination with the integrated lox site and a modifying sequence to convert the region of the immunoglobulin loci to the modified region.

Abstract: The subject invention provides non-human mammalian hosts characterized by inactivated endogenous Ig loci and functional human Ig loci for response to an immunogen to produce human antibodies or analogs thereof. The hosts are produced by multiple genetic modifications of embryonic cells in conjunction with breeding. Different strategies are employed for recombination of the human loci randomly or at analogous host loci. Chimeric and transgenic mammals, particularly mice, are provided, having stably integrated large, xenogeneic DNA segments. The segments are introduced by fusion with yeast spheroplasts comprising yeast artificial chromosomes (YACs) which include the xenogeneic DNA segments and a selective marker such as HPRT, and embryonic stem cells.

Abstract: A method to produce a cell expressing an antibody from a genomic sequence of the cell comprising a modified immunoglobulin locus using Cre-mediated site-specific recombination is disclosed. The method involves first transfecting an antibody-producing cell with a homology-targeting vector comprising a lox site and a targeting sequence homologous to a first DNA sequence adjacent to the region of the immunoglobulin loci of the genomic sequence which is to be converted to a modified region, so the first lox site is inserted into the genomic sequence via site-specific homologous recombination. Then the cell is transfected with a lox-targeting vector comprising a second lox site suitable for Cre-mediated recombination with the integrated lox site and a modifying sequence to convert the region of the immunoglobulin loci to the modified region.

Abstract: Antibodies with fully human variable regions against a specific antigen can be prepared by administering the antigen to a transgenic animal which has been modified to produce such antibodies in response to antigenic challenge, but whose endogenous loci have been disabled. Various subsequent manipulations can be performed to obtain either antibodies per se or analogs thereof.

Abstract: The method of the invention provides the use of a replacement-type targeting construct to delete large fragments of genomic DNA by gene targeting. The replacement targeting construct, which may contain a selectable marker, is constructed to contain two regions of sequences which are homologous to the 5' and 3' flanking sequences of the targeted locus. After transfection of the targeting construct into the desired cell line, gene targeted-mediated deletions are identified by selection and further characterized. The invention is useful in any situation where one would want to create a large genomic deletion. Examples of suitable loci include MHC Class I and II antigens and immunoglobulin genes, including, for example, variable and constant region of kappa, lambda, or heavy chains.

Abstract: Switch regions derived from an immunoglobulin (Ig) gene are used to direct recombination between a targeting construct containing a promoter, a switch region (S.sub.1), and 2) a target locus minimally containing a promoter, a switch region (S.sub.2), and a target sequence.

Abstract: The subject invention provides non-human mammalian hosts characterized by inactivated endogenous Ig loci. The hosts are produced by repetitive transformations of embryonic stem cells by homologous recombination, preferably in conjunction with breeding. Different strategies are employed for recombination of the human loci randomly or at analogous host loci.

Abstract: The present invention features a method of producing a multimeric protein from a hybrid cell formed from the fusion of two or more cells, each of which cell is engineered to express one component of the multimeric protein, as well as a method for screening for successful fusion of the cells to produce a desired hybrid cell. The methods of the invention are widely applicable to the production of proteins having two or more components.