Tereza Almeida, CIBIO-InBIO/UP | December 14, 2018 - 15h30 | CIBIO-InBIO’s Auditorium, Campus de Vairão




The adaptive immune system is based on the ability of lymphocytes to identify foreign antigens produced by pathogens. The Chondrichthyes (sharks, rays and chimaeras), or Cartilaginous Fishes, is the most basal vertebrate lineage possessing the basic features of the innate and adaptive immune systems present in mammals, and thus are key taxa to understand the emergence and evolution of vertebrate adaptive immunity. These species also occupy a variety of habitats and have different lifestyles, thus they are exposed to different pathogens that may rely on different immune mechanisms. In this talk, I will present my PhD project and some preliminary results on the genetic architecture and diversity of the major histocompatibility complex (MHC) in Chondrichthyes. The MHC genes are required for adaptive immunity, specifically for the presentation of antigens to T cells. I have found a new, ancient, MHC-linked class I gene in all cartilaginous fishes, which appears to be single copy in sharks and rays (elasmobranchs), but multicopy in chimaeras (holocephalans). While the canonical peptide-binding residues are conserved in the new MHC molecule as compared to the classical MHC class I molecule, the new gene seems to be monomorphic and has a unique tissue distribution. The data suggest that the new molecule binds a unique set of peptides in all sharks rather than to diverse sets of peptides in individual sharks bound by classical class I molecules. I will discuss the new data in light of previous knowledge and assumptions and will present the open questions in the field. For instance, what is the function of this new MHC I gene? Which cell types express this molecule? I have also examined two other lineages of previously reported nonclassical class I genes in cartilaginous fish. Both are only detected in shark species, but one is multicopy and the other has a wide gene-number range. Our data suggest that early in vertebrate history there was already a division of labor among class I genes, most likely presenting antigens of different classes to different subsets of T cells.


Tereza Almeida holds a MSc in Technologic, Comparative and Molecular Genetics from University of Trás-os-Montes e Alto Douro. She is currently enrolled in the 3rd year of the BIODIV PhD program, working under the supervision of Pedro Esteves (CIBIO-InBIO, IMED), Ana Verissimo (MARCHANGE) and Martin F. Flajnik (Microbiology and Immunology, University of Maryland).



[Host: Pedro Esteves, IMED]



Image credits: Emma Hickerson