Human, antigen-specific polyclonal antibodies are in high demand for therapeutic and research applications. However, the supply of these antibodies currently comes from only human donors and cannot satisfy the demand. The application of pathogen-specific human polyclonal antibodies is limited because there are severe restrictions on the kinds of antigens and the immunization protocols that can be used in humans. In the attempt to resolve the issue of the supply of antigen-specific, human polyclonal antibodies, transgenic for human Ig (hIg) animals were created. The most sufficient and promising model was the human artificial chromosome (HAC) transgenic animal. This model was successful due to the most efficient transferring vector CS20, comprising the entire unrearranged human heavy (1.5MB) and lambda locus (1 MB). In order to produce a large quantity of polyclonal hIg, cloned HAC transgenic cattle were created. Highly human-specific and bovine non-cross reactive, polyclonal bovine anti-human antibody and sensitive solid phase ELISA were created to determine, quantify, and characterize hIg in the sera of HAC transgenic cattle. Using the assay, that have been developed in this study; it was found that the majority of the HAC cattle produce hIg. It was also found that both heavy and light chains of hIg are produced by HAC bovines. The heavy chain of hIg undergoes class switching to the IgG and its half-life is 30 days, which is longer than hIgG in humans (21 days) or bovine IgG in bovines (19 days). Highly human-specific and bovine non-cross reactive monoclonal antibodies for the characterization of hIg produced by HAC cattle were created to recognize hIg heavy chain classes/subclasses and light chains. Analysis of the human V lambda genes sequences derived from HAC transgenic cattle demonstrated that human genes undergo extensive rearrangement and somatic hypermutation following normal Ig patterns. This study has demonstrated that hIg produced by HAC cattle diversifies according to normal Ig patterns and undergoes class switching to IgG. The half-life of hIgG is sufficiently long for protection from pathogens of the homozygous Ig deficient HAC cattle, and for harvesting of human IgG. HAC transgenic cattle can be potential donors of human polyclonal Ig.