WALSH, C.J.*; LUER, C.A.; BODINE, A.B.; LITMAN, G.W.; ANDERSON, M.K.; MIRACLE, A.L.; Mote Marine Laboratory, Sarasota, FL; Mote Marine Laboratory, Sarasota, FL; Clemson Univ., Clemson, SC; Univ. of South Florida Children’s Research Institute, St. Petersburg, FL; Sunnybrook and Women’s College Health Sciences Centre, Toronto, Ontario; U.S. Environmental Protection Agency, Cincinnati, OH: The Immune System of Elasmobranch Fishes

Reports that elasmobranchs (sharks, skates, and rays) may have a low incidence of disease has stimulated interest in understanding the role of their immune system in this apparent resistance. Although research in this area may potentially translate into applications for human health, an initial understanding of the basic components of the elasmobranch immune system is essential. As in higher vertebrates, elasmobranch fishes possess thymus and spleen, but in the absence of bone marrow and lymph nodes, these fish have evolved unique lymphomyeloid tissues, namely epigonal and Leydig organs. TCR genes and genes associated with T-cell development are expressed in the elasmobranch thymus, implicating this tissue as a primary source of T-cells. Expression of immunoglobulin genes is more complex, with simultaneous expression of these genes in spleen, epigonal and Leydig organs suggesting multiple sites for B-cell development. The presence of rearranging antigen receptor genes along with recombinase-activating genes and polymorphic MHC genes that encode for antigen presentation structures suggest that elasmobranchs are the earliest phylogenetic group to possess the components necessary for an adaptive immune system. Ongoing studies to identify immune regulatory factors in the media conditioned by short-term cultures of epigonal cells have resulted in the isolation of bioactive compounds with potent growth inhibitory activity against several mammalian tumor cell lines and may represent novel cytokines with potential applications for human health.