Abstract: The invention relates to transgenic non-human animals capable of producing heterologous antibodies and methods for producing human sequence antibodies which bind to human antigens with substantial affinity.

Abstract: Transgenic mice having a phenotype characterized by the substantial depletion of a mature lymphocytic cell type otherwise naturally occurring in the species from which the transgenic mouse is derived. The phenotype is conferred in the transgenic mouse by a transgene contained in at least the precursor stem cell of the lymphocytic cell type which is depleted. The transgene comprises a DNA sequence encoding a lymphatic polypeptide variant which inhibits maturation of the lymphocytic cell type.

Abstract: The invention relates to transgenic non-human animals capable of producing heterologous antibodies and methods for producing human sequence antibodies which bind to human antigens with substantial affinity.

Abstract: The invention relates to transgenic non-human animals capable of producing heterologous antibodies and methods for producing human sequence antibodies which bind to human antigens with substantial affinity.

Abstract: Transgenic mice having a phenotype characterized by the substantial depletion of a mature lymphocytic cell type otherwise naturally occurring in the species from which the transgenic mouse is derived. The phenotype is conferred in the transgenic mouse by a transgene contained in at least the precursor stem cell of the lymphocytic cell type which is depleted. The transgene comprised is a DNA sequence encoding a lymphatic polypeptide variant which inhibits maturation of the lymphocytic cell type.

Abstract: The present invention provides novel methods for modifying the genome of an animal cell which typically comprise the steps of: constructing a DNA molecule in which desired sequence modifications are contained in a segment of DNA (a "targeting DNA") that is substantially isogenic with a DNA in the cell genome (a."target DNA"); introducing the targeting DNA construct into the cell (e.g., by microinjection, electroporation, transfection, or calcium phosphate precipitation); and selecting cells in which the desired sequence modifications have been introduced into the genome via homologous recombination.

Abstract: The invention relates to transgenic non-human animals capable of producing heterologous antibodies of multiple isotypes. Heterologous antibodies are encoded by immunoglobulin heavy chain genes not normally found in the genome of that species of non-human animal. In one aspect of the invention, one or more transgenes containing sequences that permit isotype switching of encoded unrearranged heterologous human immunoglobulin heavy chains are introduced into a non-human animal thereby forming a transgenic animal capable of producing antibodies of various isotypes encoded by human immunoglobulin genes. Such heterologous human antibodies are produced in B-cells which are thereafter immortalized, e.g., by fusing with an immortalizing cell line such as a myeloma or by manipulating such B-cells by other techniques to perpetuate a cell line capable of producing a monoclonal heterologous antibody.

Abstract: Transgenic mice having a phenotype characterized by the substantial absence of mature T lymphocytes otherwise naturally occurring in said mice. The phenotype is conferred in the transgenic mouse by a transgene contained in at least the precursor stem cell of the T lymphocyte which is depleted. The transgene comprises a DNA sequence encoding a T cell receptor polypeptide variant which inhibits maturation of the T lymphocyte.