Main Components of Fish Immunity: An Overview of the Fish Immune System

Abstract

Cellular immune responses consist of innate and adaptive cell-mediated immune mechanisms, where all leukocyte subpopulations are included. Among these are vital processes such as cell-mediated cytotoxicity and phagocytosis. The main cellular constituents of the fish immune system are macrophages, granulocytes, dendritic cells, NK cells, and cytotoxic T cells. This review provides the latest information on cellular defense mechanisms of fish and provides an overview of the function of the mucosal immune system in maintaining the general health of fish. Here, we discuss the fundamental ideas that underpin mucosal immune responses in teleosts, as well as the innate and adaptive immune cells and the molecules that play a role in these immune responses. Moreover, cytokine molecules and pathways in teleosts have been reported to focus on several kinds of associated immunity. Importantly, we also review antigen processing and presentation. The knowledge reported here will enable better understanding, determination, and modulation of the pathways responsible for protective immunity, thus consequently improving the health of the fish in aquaculture.

Experimental challenge of Chinook salmon withTenacibaculum maritimumandTenacibaculum dicentrarchifulfils Koch’s postulates

“…The positive correlation noted in bacterial load between external tissue (skin and gill) and anterior kidney in T. maritimum challenged fish further proves the likelihood of hematogenous spread of pathogen. The anterior kidney in fish is a known lymphoid organ and a site for antigen presentation, therefore during a Tenacibaculum infection, phagocytic antigen presenting cells may also be responsible for the presence of nucleic acid in this tissue [108]. This appears consistent with the observations of Frisch, Småge (8), who found T. maritimum was detected by real-time RT PCR in several internal organs, however fish were dying with no gross internal abnormalities other than "yellow plaques" on the jaw in experimentally induced mouth rot in Atlantic salmon smolts.…”

Molecular identification and in silico functional characterization of a histone H2A derived antimicrobial peptide from Tilapia lake virus (TiLV) infected Nile tilapia (Oreochromis niloticus)

“…Therefore, AMPs inhibit viral fusion by directly interacting with the viral envelope and host cell surface molecules thereby preventing infection and spread [54]. In marine vertebrates like shes, the cellular components of innate immune system are essential for preventing pathogens and for providing resistance to infections because of delayed adaptive immune response [55]. In this case, it is likely that TiHip would have been produced as effector molecules of innate immunity of tilapia to act against enveloped TiLV.…”

Surviving on limited resources: effects of caloric restriction on growth, gene expression and gut microbiota in a species with male pregnancy (Hippocampus erectus)

“…3). TLRs 21 and 22 lead to upregulation of inflammatory pathways 86,87 , same as several chemokines, tnf, irf5 , and M17 (analogous to mammalian IL-6) which are all strong pro-inflammatory cytokines in fish 89,91,92 . This might be attributed to how females prime their eggs for transgenerational plasticity.…”