Functional aspects of fish lymphocytes

Abstract

After almost 40 years of studies in comparative immunology, some light has been shed on the evolutive immunobiology of vertebrates, and experimental evidences have shown that acquired immunity, defined by somatic recombination of antigen-binding molecules and memory, is an achievement as ancient as jawless vertebrates. However, the molecular processes generating antigen receptors evolved independently between jawless and jawed fishes, and produced lymphocytic cells with similar functions but employing different sets of genes. In recent years, data have been provided describing some in vitro and in vivo functional responses of fish lymphocytes. After a long gap, the number of specific markers for fish lymphocytes is increasing, thus allowing a first characterisation of lymphocyte subsets. Overall, in the near future it will be possible to open a new chapter in fish immunology and investigate functional immunity of lymphocyte responses by combining the extensive knowledge on immune gene products with markers for molecules and cells. The present review summarizes current knowledge on functional features of fish lymphocytes.

Keywords: 5-HT3; 5-hydroxytriptamine; CDR; CMC; CTL; Comparative immunology; ConA; Fish; Functional; HEL; ISH; ITAM; ITIM; Ig; LPS; Lymphocytes; MHC; MIF; MLR; NCC; NKT; PBL; PHA; Poly I:C; RAG; Receptors; T cell receptor; TLR; TR; cell-mediated cytotoxicity; complementarity-determining region; concanavalin A; cytotoxic T lymphocytes; hen egg lysozyme; immunoglobulin; immunoreceptor tyrosine-based activation motif; immunoreceptor tyrosine-based inhibition motif; in situ hybridization; lipopolysaccharide; mAb; macrophage-inhibitory factor; major histocompatibility complex; mixed leucocyte reaction; monoclonal antibody; natural cytotoxic cells; natural killer T cells; peripheral blood leukocytes; phytohemoagglutinin (generally from beans); polyinosine–cytidine; recombination-activating gene; toll-like receptor.