Lymphocytes of Teleosts

Increasing evidences suggest that there is a great degree of similarity in the morphologi- cal and functional organization of immune defences across jawed vertebrates, and lymphocytes are among the most conserved elements. Some peculiarities make lymphocytes unique cells, they contain enzymes (RAGs) able to recombine somatically genome sequences, genome sequences prone to recombination (Ig, TcR), and MHC machinery able to recognize extracellular and intracellular antigens, thus representing an extraordinary and efficient evolutionary machinery to fight nonself. The evolutionary success of lymphocytes is evident in the similarities between cell populations and physiological functions conserved among vertebrates. Teleost fish represent the base of the evolutionary pathway that shaped lymphocyte functions, and this review summarizes the available knowledge on fish lymphocyte populations and subpopulations, and their main physiological features.