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Comparative Immunology
Published in Julius P. Kreier, Infection, Resistance, and Immunity, 2022
In 1884, Eli Mechnikoff discovered phagocytosis while examining starfish larvae. He showed that mobile cells attacked rose thorns introduced into the coelom of these larvae. Several different types of phagocytic cell are recognized in invertebrates; the most important are blood leukocytes (hemocytes) and body cavity cells (coelomocytes). These cells act like mammalian phagocytes and undergo chemo-taxis, adherence, ingestion, and digestion. They contain proteases and may produce reactive oxygen radicals. Some phagocytic cells may be hemostatic and can aggregate in and plug wounds. In cases where these cells are unable to control invaders by phagocytosis, granulomas may form.
The Immune System and its Function
Published in Istvan Berczi, Pituitary Function and Immunity, 2019
The ability of responding rapidly to infectious agents, or to other foreign materials (antigens), with the synthesis of specific proteins (antibodies) and/or production of specific effector cells has been encountered only in vertebrates.1 This adaptive immune response is of vast importance for survival as it constitutes the principal means of defense against pathogenic microorganisms, parasites, and possibly against neoplastic disease.2 Our knowledge of immunity in invertebrates is rudimentary, but it appears that these animals can also recognize foreign materials. Transplant failures in coelentarates were attributed to the existence of a defense mechanism similar to that of graft rejection in higher animals.3 Earthworms are able to destroy grafts from donors of the same or different species. This graft rejection is characterized by specificity and anamnesis and can be transferred with immune cells (coelomocytes).4–6 Insects can also develop immunity rapidly with the appearance of nonprotein antibacterial factors produced by antigenic stimulation, while in general, arthropods fail to recognize tissue grafts as foreign.7
TRPML Subfamily of Endolysosomal Channels
Published in Bruno Gasnier, Michael X. Zhu, Ion and Molecule Transport in Lysosomes, 2020
Nicholas E. Karagas, Morgan A. Rousseau, Kartik Venkatachalam
The commonly studied invertebrates, Drosophila melanogaster and Caenorhabditis elegans, possess single TRPML encoding genes – trpml and coelomocyte uptake defective-5 (cup-5), respectively (Fares and Greenwald, 2001; Venkatachalam et al., 2008). The worm cup-5 mutants exhibit maternal-effect embryonic lethality and endolysosomal accumulation. Flies lacking trpml exhibit defects in completion of autophagy with a concomitant build-up of endolysosomes in a wide range of tissues, high rates of pupal lethality, age-dependent neurodegeneration, and locomotor impairment. The MLIV flies also exhibit defects in glutamatergic synapse development and neurotransmission (Venkatachalam et al., 2008; Wong et al., 2015). Interestingly, the neurological phenotypes in the MLIV flies are a result of a complex interplay between neurons and phagocytic cells (Venkatachalam et al., 2008). First, cell autonomous endolysosomal defects in neurons led to accumulation of damaged mitochondria and diminished cell viability. A secondary, non-cell autonomous effect in phagocytic cells such as glia was triggered by the dying neurons and led to neuroinflammation. Remarkably, reintroduction of wild-type trpml in only the phagocytic cells was sufficient to significantly delay the locomotor defects and attendant lethality. These findings led to the intriguing proposal that bone marrow transplantation to introduce functional phagocytic cells such as microglia in patients lacking TRPML1 could delay the onset of MLIV – a concept that was successfully validated in a mouse model of MLIV (Walker and Montell, 2016).
Cationic polystyrene nanoparticle and the sea urchin immune system: biocorona formation, cell toxicity, and multixenobiotic resistance phenotype
Published in Nanotoxicology, 2018
L. F. Marques-Santos, G. Grassi, E. Bergami, C. Faleri, T. Balbi, A. Salis, G. Damonte, L. Canesi, I. Corsi
Invertebrate animals have an immune response noticeably distinct from vertebrates, which is not adaptive and defined as a classical innate immune system. In sea urchins, the immune response consists of humoral and cellular response (Smith et al. 2010). The sea urchins’ humoral response is mediated by molecules present in the body fluids, essentially in the celomic fluid (CF), which fills the perivisceral celomic cavity and whose main soluble protein is the toposome precursor subunit (Cervello and Matranga 1989). Cell-mediated immune response, in sea urchins, is associated to free circulating cells, which are classified in three cell types: phagocytes (the most abundant), vibratile cells, white and red amebocytes (Pinsino and Matranga 2015). Coelomocytes are present in the CF and in the water vascular system, circulatory system, conjunctive tissue, and other organs
Gold nanoparticles ingested by oyster larvae are internalized by cells through an alimentary endocytic pathway
Published in Nanotoxicology, 2018
Seta Noventa, Christian Hacker, Ana Correia, Claudia Drago, Tamara Galloway
Residual bodies containing NPs were frequently observed inside phagocytic coelomocytes, distinguished by their dense granular cytoplasm and abundant vacuoles, lining the shell or the mantle (Figure 5). In contrast to the phagocytes of the adult stage, these cells have rarely been studied in the larval phases (Elston 1980a, 1980b; Wikfors and Smolowitz 1995) and their physiology and functions are not well known. They are suggested to be generated by the mantle tissue during the prodissoconch I stage (i.e. the larval phase studied here) and undergo differentiation while still incorporated within the mantle tissue or in the fluid of the visceral cavity. At their mature stage, they are found inside the visceral cavity, suspended in the fluid and attached to the luminal surface (Elston 1980a, 1980b) and the connective tissue around the digestive diverticula (Yonge 1926b), where they remove foreign material and host tissue debris absorbed by the digestive gland and released into the visceral cavity. The finding of NP containing residual bodies inside these cells unveils a crossroads in the pathway of internalized NPs. The NPs can be translocated here from the digestive gland to undergo further processing and distribution and/or to be eliminated via an alternative ejection route. In fact, obsolescent, dying or infected phagocytes are extruded from the body via diapedesis, a phenomenon occurring in the larval phases through the velum and associated membranes (Elston 1980b). More study is needed to clarify the role of these cells in the alimentary pathway and in the fate of non-nutritious particles.