FOUR STABLE CLASS I LINEAGES IN CARTILAGINOUS FISHES
Tereza Almeida, Universidade do Porto
Tereza Almeida1,2, Ana Verissimo 1,3, Pedro Esteves 1,2, Yuko Ohta4, Martin Flajnik4
1CIBIO-InBIO, Centro de Investigacão em Biodiversidade e Recursos Genéticos, Campus Agrário de Vairão, Universidade do Porto, Vairão, Porto, Portugal;
2Departamento de Biologia, Faculdade de Ciências da Universidade do Porto, Porto, Portugal;
3Virginia Institute of Marine Science, College of William and Mary, Gloucester Point, Virginia, USA
4Department of Microbiology and Immunology, University of Maryland at Baltimore, Baltimore, Maryland, USA.
Chondrichthyes (sharks, rays and chimaeras) is the most basal vertebrate lineage possessing the basic features of the adaptive immune systems present in mammals, and thus is a key taxon to understand the emergence and evolution of vertebrate adaptive immunity. We will present novel results on the diversity of genetic lineages of the major histocompatibility complex (MHC) in Chondrichthyes. A new, MHC-linked nonclassical class I lineage (UDA) was found in all cartilaginous fishes, which is a single copy gene in Elasmobranchs but multicopy in Holocephalans. This new gene is apparently monomorphic and has a unique tissue distribution. The resulting protein is predicted to bind to a unique set of peptides in all Elasmobranchs rather than to allele-specific sets of peptides as is the case for polymorphic MHC classical class I molecules. At the cellular level, we found that UDA is expressed in gill predominantly at the luminal epithelium surface. Two other lineages of previously reported nonclassical class I genes in cartilaginous fishes were also examined in detail, of which one (UBA) is present in all species tested and is generally multicopy, while the other (UCA) is elasmobranch-specific and shows a wider gene number range. Our data suggest that early in vertebrate history there was a division of labor among MHC class I genes, most likely presenting antigens of different types to different subsets of T cells.