Shark immune system: A review about their immunoglobulin repertoire

In the past few decades, the literature about the immune system of vertebrates has increased thanks to the research about new therapies and new biomolecules able to treat or eradicate many human autoimmune diseases. Researchers found that immunoglobulins (Igs) are the most versatile biomolecules able to recognize almost every existing epitope with their binding domains. Phylogenetically, the most recent vertebrates exhibit the greatest sequence diversification in their Igs to extend their ability to distinguish different antigens. Among cartilaginous fishes, the most ancient vertebrates on phylogenetic history, sharks possess four types of Igs with similar pathways to extend sequence diversity and binding domains variability. Their Ig new antigen receptor (IgNAR) represents one of the most versatile and small Ig type upon all other species. The shark species are fundamental sources of new therapeutic receptors lending a further step to treatments against several human diseases. The aim of this review is to analyze sharks Igs, focusing on IgNARs for each species.