||Ovalbumin (abbreviated OVA) is the main protein found in egg white, making up 60-65% of the total protein. Ovalbumin displays sequence and three-dimensional homology to the serpin superfamily, but unlike most serpins it is not a serine protease inhibitor. The function of ovalbumin is unknown, although it is presumed to be a storage protein. OVA is also the best characterized and the first antigen proteins used as a transgene to make transgenic mice. Many different transgenic mouse models have systemic OVA expression driven by the ubiquitously expressed b-actin promoter or tissue-specific OVA expression with insulin promoter to drive the transgene expression, for studying type I diabetes, or in different isoforms, secreted or cell-membrane associated, and more recently as inducible transgene models. These C57BL/6 mice, BALB/c mice models are well characterized, and have contributed to our understanding of immunogenicity and tolerance by the OVA model.