The present invention provides ungulate animals, tissue and organs as well ascells and cell lines derived from such animals, tissue and organs, which lackexpression of functional endogenous immunoglobulin loci. The present inventionalso provides ungulate animals, tissue and organs as well as cells and celllines derived from such animals, tissue and organs, which express xenogenous,such as human, immunoglobulin loci. The present invention further providesungulate, such as porcine genomic DNA sequence of porcine heavy and lightchain immunogobulins. Such animals, tissues, organs and cells can be used inresearch and medical therapy. In addition, methods are provided to preparesuch animals, organs, tissues, and cells.
