chapter  13
27 Pages

The Immune System of Sharks, Skates, and Rays

ByCarl A. Luer, Catherine J. Walsh, and Ashby B. Bodine

CONTENTS 13.1 Introduction .................................................................................................................................. 369 13.2 Cells of the Elasmobranch Immune System ............................................................................... 370

13.2.1 Lymphocytes ................................................................................................................... 370 13.2.2 Granulocytes.................................................................................................................... 371 13.2.3 Monocytes and Macrophages ......................................................................................... 372 13.2.4 Thrombocytes .................................................................................................................. 373

13.3 Lymphomyeloid Tissues............................................................................................................... 373 13.3.1 Thymus............................................................................................................................ 374 13.3.2 Spleen .............................................................................................................................. 374 13.3.3 Epigonal and Leydig Organs .......................................................................................... 375 13.3.4 Miscellaneous Sites......................................................................................................... 377

13.4 Natural or Innate Immunity ......................................................................................................... 377 13.4.1 Nitric Oxide..................................................................................................................... 377 13.4.2 Complement and Inflammation ...................................................................................... 378 13.4.3 Phagocytosis and Pinocytosis ......................................................................................... 378 13.4.4 Nonspecific Cytotoxic Cells ........................................................................................... 379

13.5 Specific or Adaptive Immunity .................................................................................................... 380 13.5.1 Humoral Immunity.......................................................................................................... 380 13.5.2 Cell-Mediated Immunity................................................................................................. 380 13.5.3 Immune System Genes ................................................................................................... 381 13.5.4 Cytokine-Like Molecules................................................................................................ 382

13.6 Ontogeny of the Elasmobranch Immune System........................................................................ 382 13.6.1 Organogenesis of Lymphomyeloid Tissues .................................................................... 383 13.6.2 Embryonic Expression of Immune Regulatory Genes................................................... 384

13.7 Experimental Immunology........................................................................................................... 385 13.7.1 In Vitro Culture of Elasmobranch Immune Cells........................................................... 385 13.7.2 Experimental Induction of Apoptosis ............................................................................. 385 13.7.3 RNA in Situ Hybridization ............................................................................................. 386 13.7.4 Transplantation Studies ................................................................................................... 386 13.7.5 Effects of Ionizing Radiation on Elasmobranch Immune System................................. 387

13.8 Future Directions.......................................................................................................................... 388 Acknowledgments.................................................................................................................................. 389 References .............................................................................................................................................. 389

unique glimpses into the evolution of functional systems that may have had their origins during the critical transition from jawless to jawed vertebrates. A prime example is the immune system, the complex scheme of recognition reactions that are responsible for distinguishing “self” from “non-self.” In understanding the phylogeny of immunity, elasmobranch fishes fill a crucial niche because, in addition to utilizing basic nonspecific mechanisms of defense against invading elements, it has become apparent in recent years that sharks and their relatives are the first animal group to possess all the components necessary to perform the specific responses associated with adaptive immunity.