DEEP WORK

2.4.2 ComplementThe complement system is an ancient innate immune mechanism present in both vertebrate and invertebrate species. The mammalian complement system appears more developed and is composed of ∼30 different proteins, either plasma- or membraneassociated. The proteins and glycoproteins that constitute the complement system are synthesized by hepatocytes, but significant amounts are also..

2.4 Soluble mediators of immunityAn important array of regulatory mediators, highly toxic soluble molecules, degradative enzymes, and antimicrobial peptides provide strong immune humoral protection against a wide range of pathogens, orchestrate the majority of the immune mechanisms, and contribute to maintain the host homeostasis. These mediators, constitutively expressed or secreted upon induct..

2.3.2 Cells of the monocyte–macrophage lineage2.3.2.1 Monocytes and macrophagesMacrophages (and their precursors, monocytes) are the main phagocytic cells of the immune system. Tissue macrophages are present throughout the body and contribute to tissue homeostasis and immune surveillance. Upon tissue damage or infection, monocytes are rapidly recruited to the tissue where they differentiate into..

2.3 Cellular componentsThe different leukocyte types derived from the lymphoid and myeloid lineages known from mammals have also been recognized in fish, including cells morphologically and functionally equivalent to mammalian B and T lymphocytes, natural killer (NK) cells, monocytes, macrophages, neutrophils, eosinophils, mast cells, and thrombocytes (Secombes, 1996; Whyte, 2007), as well as th..

2.2 Organs, tissues, and general structures In higher vertebrates, the immune system consists of primary (lymphocyte-generating) and secondary (immune response-generating) lymphoid organs. The fetal liver, thymus and bone marrow constitute the primary lymphoid organs, while the spleen, lymph nodes, and mucosal-associated lymphoid tissue (MALT) comprise the secondary lymphoid organs.  Fish organi..

2.1 IntroductionFish are a wide and heterogeneous group of vertebrates that comprise about 40,000 species, divided into three classes: Agnatha (jawless fish represented by hagfish and lampreys), Chondrichthyes (cartilaginous fish comprising sharks, rays, and skates), and Osteichthyes (bony fish). Fish heterogeneity is based on many aspects of their biology and habitats. There are fish species ad..

Other innate immunity components in fish mucusThere are also a few important components of fish epidermal mucus which play an important role in innate immunity of fishes such as C-reactive proteins (CRPs), transferrin, ALP, complement proteins, etc. CRPs belong to a family of multifunctional proteins (pentraxins) and are capable of binding various ligands in a Ca2+ dependent binding affinity. Th..

Antimicrobial peptidesAntimicrobial peptides are increasingly recognized as a critical factor in host defence mechanism and found in organisms ranging from microbes, plants to animal species (Fernandes et al., 2004; Kennedy et al., 2009). It also plays an important role in fish when compared with mammals as fish rely more on their innate immune system (Hancock, 1997; Hancock and Scott, 2000). Fi..

Role of skin mucus components in innate immunityThe major function of the mucus appears to provide the effective separation between internal and external environment of fish, abrasion resistance and primary defense against the numerous aquatic pathogens by virtue of its components which include proteases, AMPs, lysozyme, CRP. These are discussed in detail below. ProteasesProtease refers to a gro..

IntroductionThe aquaculture industries with high densities of fishes are susceptible to diseases caused by many pathogens. Fish possess numerous distinct and complex defense mechanisms to protect themselves from these pathogenic infections amongst which fish skin mucus acts as the first line of physical defense against pathogens (Wang et al., 2011). The fish skin mucus provides a stable physical..