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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.
Microbial Involvement in Alzheimer’s Disease
Published in David Perlmutter, The Microbiome and the Brain, 2019
Impaired gut microbiota, also known as gut dysbiosis, can first occur in the local tissues of the gut. This impairment can then expand beyond the gut itself to a generalized systemic response with functional immune changes and subsequent neuroinflammatory responses [38–40]. The immune system may contribute to and drive the pathogenesis of Alzheimer’s and thus could also provide strategies for developing novel therapeutic approaches [38–40]. Immune cells include phagocytes or macrophages in the peripheral system and the resident microglia and astrocytes in the brain and spinal cord [41]. Recently, Wu et al. showed that the effector cells/molecules in the gut dysbiosis are the hemocytes [41], also known as the phagocytes of invertebrates. They studied the roles of enteric dysbiosis in Alzheimer’s using a Drosophila Alzheimer’s model, in which enterobacteria infection increased immune hemocyte recruitment to the brain and elevated oxidative stress levels in the brain, while triggering TNF-JNK mediated neurodegeneration and exacerbating the progression of Alzheimer’s phenotype. Interestingly, the authors also found that genetic depletion of hemocytes attenuated neuroinflammation and alleviated neurodegeneration [41]. Furthermore, this work was in line with other studies showing the role of microglia cells and astrocytes in the brain in response to changes in gut microbiota [25,26,28]. In future studies, the relationship of gut microbiota and neuroinflammation in Alzheimer’s needs to be more precisely defined to identify Alzheimer’s-specific microbial species and molecules.
Host Defense and Parasite Evasion
Published in Eric S. Loker, Bruce V. Hofkin, Parasitology, 2015
Eric S. Loker, Bruce V. Hofkin
Let us consider immunoparasitology from the perspective of the invertebrate host. As we have noted, invertebrates are generally considered to have limited repertoires of PRRs. How then can invertebrates, some of which live longer than we do, keep up with the pressures posed by their parasites, which evolve relatively quickly? One answer to this question is that invertebrates may not be quite so constrained in their ability to produce diverse PRR repertoires as first thought. Consider the example of fibrinogen-related proteins (or FREPs) produced by snails such as Biomphalaria glabrata, one of the most important intermediate hosts for the trematode Schistosoma mansoni. Although we are most familiar with fibrinogen molecules functioning in blood coagulation in vertebrates, in invertebrates fibrinogen-related molecules seem to be more involved in nonself recognition. Snail defense cells called hemocytes produce FREPs. FREPs are able to agglutinate parasite antigens, and they can act as opsonins, molecules that bind to a target and enhance phagocytosis. Consequently, binding of an opsonin to a parasite surface increases the likelihood of subsequent phagocytosis or encapsulation of the parasite. Because they are organized in tandem arrays, FREP-encoding genes can engage in gene conversion, with the result that FREPs can be diversified during the course of the snail’s ontogeny (an example of somatic diversification). As a consequence, the hemocytes within a given snail do not necessarily all express the same FREP proteins. There is some evidence to suggest that diverse FREPs interact with highly variable polymorphic mucin molecules produced by life-cycle stages of S. mansoni that infect snails. Furthermore, suppressed production of one FREP, FREP3, results in partially diminished levels of resistance to trematodes in B. glabrata. Consequently, outcomes of interactions between snails and schistosomes could be governed by interaction between parasite- and snail-produced molecules that are more specific and varied than generally conceived. Thus the standard interpretation of invertebrate immune systems as possessing but limited sets of PRRs may require some modification. Some form of diversified defense molecules have been found in several invertebrate groups such as crustaceans, snails, bivalves, insects, echinoderms, tunicates, and amphioxus.
Therapeutic apheresis in kidney diseases: an updated review
Published in Renal Failure, 2022
Yi-Yuan Chen, Xin Sun, Wei Huang, Fang-Fang He, Chun Zhang
LDL-A is a novel technique used for the treatment of nephrotic syndrome (NS), especially focal segmental glomerulosclerosis (FSGS), which selectively removes lipoprotein particles from the blood with the reinfusion of the remaining components (Figure 1(D)) [8]. There are four different techniques of LDL apheresis: IAS, dextran sulfate cellulose adsorption, heparin extracorporeal LDL precipitation, and direct adsorption of lipoprotein using hemoperfusion. All of these techniques are used for familial hypercholesterolemia, but only dextran sulfate cellulose adsorption can be used for drug-resistant NS [8]. The machine first separates plasma from the rest of the blood, and then, the Liposorber filter removes the LDL, very-low-density lipoproteins, Lipoprotein (a), and triglycerides from the plasma. Finally, the hemocytes and purified plasma are returned to the patients. Low blood pressure is the most common adverse effect associated with LDL-A.
Immunothrombosis and thromboinflammation in host defense and disease
Published in Platelets, 2021
Kimberly Martinod, Carsten Deppermann
Platelets are no longer seen as single-purpose single-use cell fragments. Today we know that in fact they interact with most cells of the (innate) immune system and release a plethora of cytokines to stimulate the immune response at sites of vascular injury. In that, they are much like hemocytes, their ancient precursor found in horseshoe crabs - a living fossil that already existed 445 million years ago. Hemocytes are nucleated granular cells with combined innate immune cell/platelet function and the only circulating blood cells in horseshoe crabs. They can fight infections and cause coagulation of the hemolymph to seal off infected or injured vessels. These intriguing similarities indicate that there are probably more immune cell functions left in the platelet than most people today are aware of and probably some more new roles to be discovered.
Mechanisms of nanotoxicity – biomolecule coronas protect pathological fungi against nanoparticle-based eradication
Published in Nanotoxicology, 2020
Roland H. Stauber, Dana Westmeier, Madita Wandrey, Sven Becker, Dominic Docter, Guo-Bin Ding, Eckhard Thines, Shirley K. Knauer, Svenja Siemer
Currently, research heavily relies on murine models for studying the activity of nano-based antimicrobials as well as determining nanotoxicology (Docter, Westmeier, et al. 2015; Westmeier, Hahlbrock, et al. 2018). However, there is a growing public consciousness demanding alternative experimental models, as there are ethical, financial, and logistical problems connected with the use of mammals. Galleria mellonella can be infected by numerous microorganisms including fungi or bacteria, and thus is suggested to investigate infections and their therapies (Tsai, Loh, and Proft 2016; Siemer, Westmeier, et al. 2018). Galleria mellonella larvae can be easily and inexpensively obtained in large numbers and have a short life cycle. While lacking a typical vertebrate adaptive immune response, insects possess well-developed innate responses with remarkable similarities to vertebrates. In particular, their antifungal immunity also involves cellular and humoral components. The hemolymph system contains different types of hemocytes, important for recognition and elimination of microorganisms. Moreover, insects and humans have evolutionary conserved antimicrobial peptides, including defensins (Jiang et al. 2018; Gomez-Lopez et al. 2014; Ramarao, Nielsen-Leroux, and Lereclus 2012). Recently, we found that NM-coatings acquired in the environment reduce the sensitivity of A. fumigatus spores against defensins, resulting in reduced uptake and clearance by the immune defense system and ultimately enhancing the severity of fungal lung infections (Westmeier, Solouk-Saram, et al. 2018).