From IgZ to IgT: A Call for a Common Nomenclature for Immunoglobulin Heavy Chain Genes of Ray-Finned Fish.

Ray-finned fishes comprise more than half the *60,000 known vertebrate species, and are pivotal to the functionality of aquatic ecosystems and success of global multibillion dollar industries. Understanding ray-finned fish immune systems is essential to predicting how species will respond to known or emergent pathogens as well as to the development of effective vaccines for aquaculture. However, the diversity of species, including in aquaculture, necessitates that immunology and translational medicine research groups investigating the immune system in one or a number of species employ a common language for describing homologous immune components. Unfortunately for Immunoglobulin (Ig) genes that encode antibodies, this has not been the case. Ig genes are restricted to jawed vertebrates (gnathostomes) with all lineages encoding common heavy chains IgM and IgD (aka IgW in cartilaginous fish, lungfish, and coelacanths). Before 2005, it was believed that bony fish encoded only IgM and IgD. In 2005, Hansen et al. described a new Ig heavy chain encoded within the rainbow trout heavy chain locus and named it IgT for ‘‘teleost.’’ However, during the