Primitive Antibodies

University Of Arizona, Tucson AZ

Investigators

Abstract

A grant has been awarded to John J. Marchalonis, Ph.D. for studies on "Primitive Antibodies". This project addresses the molecular basis of diversification of the recognition molecules that are essential for the generation of specific immunity. The project focuses upon the immune system of sharks because these are the most primitive vertebrates to share with humans the combinatorial immune response. This is based uniquely upon the recombination of gene segments to generate the variability in antigen receptor molecules present in serum and on blood cells. Sharks, which arose approximately 450 million years ago, like humans have immunoglobulins (also termed antibodies), T-cell receptors (TCRs), major histocompatability antigens (MHC), and recombination activating genes (RAGs) that are required to allow rearrangement of the gene segments making up the antibodies and T-cell receptors. The project will address both conserved and unique features of the combinatorial system of carcharhine sharks to elucidate the molecular underpinning of combinatorial immunity as it is expressed in all vertebrates. The project includes three major areas of focus: The first is the complete characterization of the shark RAG locus with emphasis upon its evolutionary emergence and functional similarities and differences to the molecular homologs found in mammals and other higher vertebrates. The second major area of concentration is the characterization of the genes specifying the alpha/beta and gamma/delta T-cell receptors of carcharhine sharks including their diversity and gene organization, and the construction of recombinant single chain TCRs for functional and structural analyses. Because of the pronounced differences in organization of shark and mammalian antibody gene segments, it is crucial to determine the arrangement of shark TCR genes. The third aim tests the generality of clonal selection theory by determining whether sharks which have a cassette organization of antibody gene as opposed to translocons of higher vertebrates show clonal restriction in their antibody forming lymphocytes. These studies are directed towards applying molecular and protein chemical technologies to obtain precise answers to fundamental problems of the system as it obtains in all vertebrates, with implications for defense against invading pathogens, cancers and immunological dysfunction in autoimmunity.