Process Of Phagocytosis Research Articles

Vesicles Generated during Storage of Red Blood Cells Enhance the Generation of Radical Oxygen Speciesin Activated Neutrophils

Erythrocytes are known to shed vesicles in vivo, under various conditions in vitro, and, with impact for transfusion medicine, during storage of red blood cell concentrates (Vsto vesicles). Vsto vesicles of blood transfusions have been shown to deliver glycosylphosphatidylinositol-linked proteins to recipient erythrocytes, to display prothrombotic activity, and to have an inhibitory effect on macrophages. The interaction of Vsto vesicles with and their effect on neutrophilic granulocytes has not yet been studied in detail. Fluorescentlylabeled Vsto and calcium-induced vesicles were preparedin order to study the uptake of labeled vesicular components by neutrophils as compared to the process of phagocytosis of zymosan using flow cytometry and confocal microscopy. The activating effect of Vsto vesicles on neutrophils was addressed by a luminometric assay for stimulated radical oxygen species (ROS) generation. Coincubation of vesicles and neutrophils results in a transfer of vesicular components to the cells. This uptake is different from a phagocytotic process and is enhanced upon interference with the cellular actin cytoskeleton. Preincubation of neutrophils with Vsto vesicles results in an enhanced ROS generation by neutrophils, which is further increased upon fMLP stimulation and during zymosan phagocytosis. The activating effect of Vsto vesicles on neutrophils might be due to the specific accumulation of lysophospholipidsin Vsto vesicles and should be considered as a possible contributor to the pathogenesis of transfusion-related acute lung injury.

Biochemistry of the Phagosome: The Challenge to Study a Transient Organelle

Phagocytes are specialized cells of the immune system, designed to engulf and destroy harmful microorganisms inside the newly formed phagosome. The latter is an intracellular organelle that is transformed into a toxic environment within minutes and disappears once the pathogen is destroyed. Reactive oxygen species and reactive nitrogen species are produced inside the phagosome. Intracellular granules or lysosomes of the phagocyte fuse with the phagosome and liberate their destructive enzymes. This process of phagocytosis efficiently protects against most infections; however, some microorganisms avoid their destruction and cause severe damage. To understand such failure of phagosomal killing, we need to learn more about the actual destruction process in the phagosome. This paper summarizes methods to investigate the biochemistry of the phagosome and discusses some of their limitations. In accordance with the nature of the phagosome, the issue of localization and temporal dynamics is emphasized, and recent developments are highlighted.

Some Observations on Carbon Nanotubes Susceptibility to Cell Phagocytosis

The aim of this study was to assess the influence of different types of carbon nanotubes (CNTs) on cell phagocytosis. Three kinds of carbon nanotubes: single-walled carbon nanohorns (SWCNHs), multiwalled carbon nanotubes (MWCNTs), and ultra-long single-walled carbon nanotubes (ULSWCNTs) before and after additional chemical functionalization were seeded with macrophage cell culture. Prior to biological testing, the CNTs were subjected to dispersion process with the use of phosphate buffered solution (PBS) and PBS containing surfactant (Tween 20) or dimethyl sulfoxide (DMSO). The results indicate that the cells interaction with an individual nanotube is entirely different as compared to CNTs in the form of aggregate. The presence of the surfactant favors the CNTs dispersion in culture media and facilitates phagocytosis process, while it has disadvantageous influence on cells morphology. The cells phagocytosis is a more effective for MWCNTs and SWCNHs after their chemical functionalization. Moreover, these nanotubes were well dispersed in culture media without using DMSO or surfactant. The functionalized carbon nanotubes were easily dispersed in pure PBS and seeded with cells.

Bioinformatics analysis of macrophages exposed to Porphyromonas gingivalis: implications in acute vs. chronic infections.

BackgroundPeriodontitis is the most common human infection affecting tooth-supporting structures. It was shown to play a role in aggravating atherosclerosis. To deepen our understanding of the pathogenesis of this disease, we exposed human macrophages to an oral bacteria, Porphyromonas gingivalis (P. gingivalis), either as live bacteria or its LPS or fimbria. Microarray data from treated macrophages or control cells were analyzed to define molecular signatures. Changes in genes identified in relevant pathways were validated by RT-PCR.Methodology/Principal FindingsWe focused our analysis on three important groups of genes. Group PG (genes differentially expressed by live bacteria only); Group LFG (genes differentially expressed in response to exposure to LPS and/or FimA); Group CG (core gene set jointly activated by all 3 stimulants). A total of 842 macrophage genes were differentially expressed in at least one of the three conditions compared to naïve cells. Using pathway analysis, we found that group CG activates the initial phagocytosis process and induces genes relevant to immune response, whereas group PG can de-activate the phagocytosis process associated with phagosome-lysosome fusion. LFG mostly affected RIG-I-like receptor signaling pathway.Conclusion/SignificanceIn light of the fact that acute infections involve live bacteria while chronic infections involve a combination of live bacteria and their byproducts, group PG could represent acute P. gingivalis infection while group LFG could represent chronic P. gingivalis infection. Group CG may be associated with core immune pathways, triggered irrespective of the specific stimulants and indispensable to mount an appropriate immune response. Implications in acute vs. chronic infection are discussed.

Laminin-111: A Potential Therapeutic Agent for Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) still needs effective treatments, and myoblast transplantation (MT) is considered as an approach to repair damaged skeletal muscles. DMD is due to the complete loss of dystrophin from muscles. The lack of link between the contracting apparatus and the extracellular matrix leads to frequent damage to the sarcolemma triggering muscle fiber necrosis. Laminins are major proteins in the extracellular matrix. Laminin-111 is normally present in skeletal and cardiac muscles in mice and humans but only during embryonic development. In this study, we showed that intramuscular injection of laminin-111 increased muscle strength and resistance in mdx mice. We also used laminin-111 as a coadjuvant in MT, and we showed this protein decreased considerably the repetitive cycles of degeneration, inflammatory reaction, and regeneration. Moreover, MT is significantly improved. To explain the improvement, we confirmed with the same myoblast cell batch that laminin-111 improves proliferation and drastically increases migration in vitro. These results are extremely important because DMD could be treated only by the injection of a recombinant protein, a simple and safe therapy to prevent loss of muscle function. Moreover, the improvement in MT would be significant to treat the muscles of DMD patients who are already weak.

Blood Arachidonic Acid and HDL Cholesterol Influence the Phagocytic Abilities of Human Monocytes/Macrophages

Aims: Many immunomodulators may intensify the process of phagocytosis in monocytes. Among them are the fatty acids contained in cellular membrane phospholipids. But in the available literature there are no reports on how blood fatty acids and lipoproteins can modulate the phagocytic abilities of cells. Therefore, the aim of this study was the evaluation of the phagocytic activity of monocytes isolated from the blood of healthy human subjects with defined fatty acids and lipoprotein content. Methods: Cells obtained from 24 donors were used for measuring phagocytic activity and for the quantification of serum fatty acids, total cholesterol, TG, HDL, and LDL, respectively. Phagocytosis was determined using a PHAGOTEST kit, fatty acids using a GC chromatograph, and lipids using test kits. Results/Conclusions: The analysis shows an influence of serum HDL concentrations on the process of phagocytosis in the isolated cells and suggests that the concentration of arachidonic acid in blood is a factor that determines the phagocytic ability of monocytes. Moreover, the concentration of conjugated linoleic acid trans-10 cis-12 has considerable influence on phagocytosis.

Initial receptor–ligand interactions modulate gene expression and phagosomal properties during both early and late stages of phagocytosis

The receptors engaged during recognition and phagocytic uptake of microorganisms and particles influence signaling events and diverse subcellular responses that occur during phagosome formation and maturation. However, pathogens generally have multiple ligands on their surface, making it difficult to dissect the roles of individual receptors during phagocytosis. Moreover, it remains elusive to which extent receptor–ligand interactions and early binding events define the subsequent intracellular fate of phagosomes. Here, we used latex beads coupled to single ligands, focusing on immunoglobulin G, mannan, bacterial lipopolysaccharides and avidin, and monitored: (1) phagocytic uptake rates, (2) fusion of phagosomes with lysosomal compartments, (3) the gene expression profile during phagocytosis, (4) the protein composition of mature phagosomes and (5) time-dependent dynamics of protein association with phagosomes in J774.A1 mouse macrophages. The differently coated latex beads were internalized at different rates and exhibited different kinetics of phagolysosomal fusion events dependent on their specific ligand. Furthermore, less than 60% of identified phagosomal proteins and only 10–15% of changes in gene expression were common to all investigated ligands. These findings demonstrate that each single ligand induced a distinct pattern of genes and a different protein composition of phagosomes. Taken together, our data argue that phagocytic receptor-specific programs of signaling events direct phagosomes to different physiological states and support the existence of a specific receptor–ligand ‘signature’ during the whole process of phagocytosis.

Cell-in-cell Structures Formed between Human Cancer Cell Lines and the Cytotoxic Regulatory T-cell Line HOZOT

We previously established a novel cell line, termed HOZOT, derived from umbilical cord blood mononuclear cells that is characterized as a human cytotoxic regulatory T (Treg) cell line with a FOXP3(+)CD4(+)CD8(+)CD25(+) phenotype. Here, we describe a new property of HOZOT cells: they actively penetrate into a variety of human cancer cell lines, but not into normal cell lines, and form apparent cell-in-cell structures. In the process of cell penetration, we observed that HOZOT cells adhered to target cells seemed to first insert their nuclei into the cytoplasm of target cells, distinct from the process of phagocytosis. In addition, blocking experiments showed that major histocompatibility complex class I is one of the target cell recognition molecules for HOZOT cells. Furthermore, we propose that cell-in-cell structures between HOZOT cells and target cancer cells could be one of the cytotoxic mechanisms of HOZOT cells.

Conglutinin - an Important Element of Natural Immunity in Ruminants (a Review)

Conglutinin represents a collectin appearing only in some mammals, including cattle. It plays an important role in resistance of hosts against microbes and parasites. It exhibits affinity toward saccharides present on the surface of bacteria, viruses, fungi and parasites and it mobilizes the mechanisms leading to their inactivation. It manifests also the unique ability of agglutinating complement- and antibody-coated erythrocytes. Moreover, it shows the ability to activate immune system cells, including the process of phagocytosis. In this review also the factors that determine the amount and activity of conglutinin in mammalian serum were presented, including environmental conditions and infectious agents, such as various types of bacteria and viruses. The broad scope of conglutinin is genetically controlled and, therefore, this collectin may constitute a useful and crucial factor in cattle husbandry.

Immunosuppressive properties of Pluchea lanceolata leaves

Objective:To investigate the immunosuppressive potential of Pluchea lanceolata 50% ethanolic extract (PL) and its bioactive chloroform fraction (PLC).Materials and Methods:Preliminary screening of the Pluchea lanceolata 50% ethanolic extract (PL) was carried out with basic models of immunomodulation, such as, the humoral antibody response (hemagglutination antibody titers), cell-mediated immune response (delayed-type hypersensitivity), skin allograft rejection test, in vitro (C. albicans method), and in vivo phagocytosis (carbon clearance test).The extract was then fractionated with chloroform, n-butanol, and water to receive the respective fractions by partitioning. These fractions were employed for flow cytometry to study the T-cell specific immunosuppressive potential of these fractions.Results:Oral administration of PL at doses of 50 to 800 mg/kg in mice, with sheep red blood cells (SRBC) as an antigen, inhibited both humoral and cell-mediated immune responses, as evidenced by the production of the circulating antibody titer and delayed-type hypersensitiviy reaction results, respectively, and the immune suppression was statistically significant (P < 0.01) in Balb/C mice. PL also decreased the process of phagocytosis both in vitro (31.23%) and ex vivo (32.81%) and delayed the graft rejection time (30.76%). To study the T-cell-specific activities, chloroform, n-butanol, and water fractions from P. lanceolata were tested for T-cell specific immunosuppressive evaluation, wherein only the chloroform fraction (PLC) showed significant (P < 0.01) suppression of CD8+ / CD4+ T-cell surface markers and intracellular Th1 (IL-2 and IFN-Y) cytokines at 25 – 200 mg/kg p.o. doses. PLC, however, did not show significant suppression of the Th2 (IL-4) cytokine.Conclusion:The findings from the present investigation reveal that P. lanceolata causes immunosuppression by inhibiting Th1 cytokines.

Bigraphical models for protein and membrane interactions

We present a bigraphical framework suited for modeling biological systems both at protein level and at membrane level. We characterize formally bigraphs corresponding to biologically meaningful systems, and bigraphic rewriting rules representing biologically admissible interactions. At the protein level, these bigraphic reactive systems correspond exactly to systems of kappa-calculus. Membrane-level interactions are represented by just two general rules, whose application can be triggered by protein-level interactions in a well-de\"ined and precise way. This framework can be used to compare and merge models at different abstraction levels; in particular, higher-level (e.g. mobility) activities can be given a formal biological justification in terms of low-level (i.e., protein) interactions. As examples, we formalize in our framework the vesiculation and the phagocytosis processes.

An electrostatic switch displaces phosphatidylinositol phosphate kinases from the membrane during phagocytosis

Plasmalemmal phosphatidylinositol (PI) 4,5-bisphosphate (PI4,5P(2)) synthesized by PI 4-phosphate (PI4P) 5-kinase (PIP5K) is key to the polymerization of actin that drives chemotaxis and phagocytosis. We investigated the means whereby PIP5K is targeted to the membrane and its fate during phagosome formation. Homology modeling revealed that all PIP5K isoforms feature a positively charged face. Together with the substrate-binding loop, this polycationic surface is proposed to constitute a coincidence detector that targets PIP5Ks to the plasmalemma. Accordingly, manipulation of the surface charge displaced PIP5Ks from the plasma membrane. During particle engulfment, PIP5Ks detached from forming phagosomes as the surface charge at these sites decreased. Precluding the change in surface charge caused the PIP5Ks to remain associated with the phagosomal cup. Chemically induced retention of PIP5K-gamma prevented the disappearance of PI4,5P(2) and aborted phagosome formation. We conclude that a bistable electrostatic switch mechanism regulates the association/dissociation of PIP5Ks from the membrane during phagocytosis and likely other processes.

Live and lyophilized Lactobacillus species elicit differential immunomodulatory effects on immune cells

To study the mechanism of action of the lactobacilli, splenocytes were incubated with lactobacilli. We compared the ability of live and lyophilized Lactobacillus casei, Lactobacillus rhamnosus GG and Lactobacillus delbrueckii ssp. bulgaricus to modulate the production of interleukin 12p40 (IL-12p40), tumor necrosis factor alpha and IL-10 by splenocytes from C57BL/6 and BALB/c mice. Blocking contact between lactobacilli and immune cells abrogated all cytokine production. Toll-like receptor 2 (TLR2) was partially responsible, but not TLR4 or TLR9, for the induction of cytokine production in splenocytes. All cytokine production declined to basal levels when bacterial phagocytosis was inhibited. This shows that lactobacilli stimulation of cytokine production in splenocytes requires the process of phagocytosis and engagement of TLR2, but not TLR4 or TLR9.

Probing Macrophage Activity with Carbon‐Nanotube Sensors

Electronic sensors based on individual single-walled carbon nanotubes (SWNTs)provideanexcellent opportunity toexpand the existing set of electrical probes available for single-cell studies with a versatile high-sensitivity probe of nanometer dimension. SWNTs have been shown to function both as nanoscale electrochemical sensors and as electrostatic fieldeffect-transistor (FET) sensors. The biological processes occurring inandaroundlivingcellsarecommonlyofelectrostatic and/or electrochemical nature, and can thus potentially be probed with SWNT sensors. Importantly, SWNTs have a quasione-dimensional cylindricalgeometry.Witha lengthof several micrometers, a SWNTcan span a single cell, while its diameter is of the order of one nanometer, directly comparable to the size of singleproteins. In comparisonwith current electrical probes that have lateral dimensions comparable to single cells, SWNT probes can have a higher spatial resolution and impose a largely reduced physical perturbation when in contact with or puncturing through the membrane of a single cell. Here we present our first studies of SWNT sensors as electrical probes to interrogate single macrophage cells and probe cellular activity. As part of the immune system, macrophages can ingest and digest pathogens in a process known as phagocytosis. We coat SWNT sensors with antibodies to stimulate macrophages to attach to, ingest, and attempt to digest the sensors. During phagocytosis a multitude of processes occur, including binding of antibodies to membrane-bound receptors, changes in cell morphology, pH changes, and the production of cytotoxic molecules. By employing antibody-coated SWNTs in an electrolyte-gated transistor configuration, we aim to follow the process of phagocytosis in real-time by simultaneously monitoring both changes in transistor conductance (FET signal) and changes in

Neuronal expression of Cd36, Cd44, and Cd83 antigen transcripts maps to distinct and specific murine brain circuits

Cells recruited by the innate immune response rely on surface-expressed molecules in order to receive signals from the local environment and to perform phagocytosis, cell adhesion, and others processes linked to host defense. Hundreds of surface antigens designated through a cluster of differentiation (CD) number have been used to identify particular populations of leukocytes. Surprisingly, we verified that the genes that encode Cd36 and Cd83 are constitutively expressed in specific neuronal cells. For instance, Cd36 mRNA is expressed in some regions related to circuitry involved in pheromone responses and reproductive behavior. Cd44 expression, reanalyzed and detailed here, is associated with the laminar formation and midline thalamic nuclei in addition to striatum, extended amygdala, and a few hypothalamic, cortical, and hippocampal regions. A systemic immune challenge was able to increase Cd44 expression quickly in the area postrema and motor nucleus of the vagus but not in regions presenting expressive constitutive expression. In contrast to Cd36 and Cd44, Cd83 message was widely distributed from the olfactory bulb to the brain stem reticular formation, sparing the striatopallidum, olivary region, and cerebellum. Its pattern of expression nevertheless remained strongly associated with hypothalamic, thalamic, and hindbrain nuclei. Unlike the other transcripts, Cd83 mRNA was rapidly modulated by restraint stress. Our results indicate that these molecules might play a role in specific neural circuits and present functions other than those attributed to leukocyte biology. The data also suggest that these surface proteins, or their associated mRNA, could be used to label neurons in specific circuits/regions.

Characterization of neutrophil extracellular traps in cats naturally infected with feline leukemia virus

Feline leukemia virus (FeLV), a common, naturally occurring gammaretrovirus in domestic cats, is associated with degenerative diseases of the haematopoietic system, immunodeficiency and neoplasia. FeLV infection causes an important suppression of neutrophil function, leading to opportunistic infections. Recently, a new microbicidal mechanism named NETosis was described in human, bovine and fish neutrophils, as well as in chicken heterophils. The purpose of the present study was to characterize NETosis in feline neutrophils, as well as to evaluate neutrophil function in FeLV naturally infected symptomatic and asymptomatic cats through the phagocytosis process, release of neutrophil extracellular traps (NETs) and myeloperoxidase (MPO) activity. The results showed that feline neutrophils stimulated with protozoa parasites released structures comprising DNA and histones, which were characterized as NETs by immunofluorescence. Quantification of NETs after neutrophil stimulation showed a significant increase in NET release by neutrophils from FeLV(-) and FeLV(+) asymptomatic cats compared with FeLV(+) symptomatic cats. Moreover, the number of released NETs and MPO activity in unstimulated neutrophils of FeLV(+) symptomatic cats were higher than those in unstimulated neutrophils from FeLV(-) and FeLV(+) asymptomatic cats. This study reports, for the first time, NET release by feline neutrophils, along with the fact that NET induction may be modulated by a viral infection. The results indicate that the NET mechanism appears to be overactivated in FeLV(+) cats and that this feature could be considered a marker of disease progression in FeLV infection.

Down-Regulation of Platelet Surface CD47 Expression in Escherichia coli O157:H7 Infection-Induced Thrombocytopenia

BackgroundPlatelet depletion is a key feature of hemolytic uremic syndrome (HUS) caused by Shiga toxin-producing Escherichia coli (STEC) infection. The mechanism underlying STEC-induced platelet depletion, however, is not completely understood.Methodology/Principal FindingsHere we demonstrated for the first time that platelet surface expression of CD47 was significantly decreased in C57BL6 mice treated with concentrated culture filtrates (CCF) from STEC O157:H7. STEC O157:H7 CCF treatment also led to a sharp drop of platelet counts. The reduction of cell surface CD47 was specific for platelets but not for neutrophil, monocytes and red blood cells. Down-regulation of platelet surface CD47 was also observed in isolated human platelets treated with O157:H7 CCF. Platelet surface CD47 reduction by O157:H7 CCF could be blocked by anti-TLR4 antibody but not anti-CD62 antibody. Down-regulation of platelet surface CD47 was positively correlated with platelet activation and phagocytosis by human monocyte-derived macrophages. Furthermore, the enhanced phagocytosis process of O157:H7 CCF-treated platelets was abolished by addition of soluble CD47 recombinants.Conclusions/SignificanceOur results suggest that platelet CD47 down-regulation may be a novel mechanism underneath STEC-induced platelet depletion, and that the interactions between CD47 and its receptor, signal regulatory protein α (SIRPα), play an essential role in modulating platelet homeostasis.

Recent Advances of Metal Binding Protein Lactoferrin as an Anti- Microbial Agent

Lactoferrin (Lf) is present in milk and gland secretions and serve as an antimicrobial function. Insufficient amounts of Lf in some secretions also appear to correlate with certain health problems. Protection against gastroenteritis is the most likely biologically relevant activity of lactoferrin. Multiple in vitro and animal studies have shown a protective effect of lactoferrin on infections with enteric microorganisms, including rotavirus, Giardia, Shigella, Salmonella and the diarrheagenic Escherichia coli. Lactoferrin has two major effects on enteric pathogens: it inhibits growth and it impairs function of surface expressed virulence factors thereby decreasing their ability to adhere or to invade mammalian cells. Lf also inhibits several species of fungi and certain parasites. This review covers the role of Lf in clearing the parasitic infections. The mechanism by which lactoferrin inhibits some parasites may be via stimulation of the process of phagocytosis, whereby immune cells engulf and digest foreign organisms. Trichomonas vaginalis is a protozoan responsible for the number one, non-viral sexually transmitted disease. In this review, we also discussed the role of Lf in cervical infections.

Phagocytosis Inhibits F-Actin-Enriched Membrane Protrusions Stimulated by Fractalkine (CX3CL1) and Colony-Stimulating Factor 1

Cryptococcus neoformans is the only encapsulated human-pathogenic fungus and a facultative intracellular pathogen that can reside in macrophages without host cell lysis. In the present study, we investigated how phagocytosis of C. neoformans affected the macrophage response to chemoattractants such as fractalkine (FKN) (CX3CL1) and colony-stimulating factor 1 (CSF-1). Phagocytosis of immunoglobulin G (IgG)-opsonized C. neoformans and IgG- or C3bi-opsonized sheep erythrocytes was performed using a RAW 264.7 subline (LR5 cells) and bone marrow-derived macrophages (BMM). The chemotactic response to FKN or CSF-1 was quantitated by measurement of the formation of F-actin-enriched membrane protrusions (ruffles), which showed that FKN or CSF-1 stimulated strong transient ruffling in both LR5 cells and BMM. This stimulated cell ruffling was inhibited by phagocytosis in an intracellular-pathogen-number-dependent manner. The inhibition of ruffling was not simply a result of reduced membrane availability since membrane sequestration by sucrose treatment did not inhibit the ruffling response. The phagocytosis process was required to inhibit ruffling as BMM from Fc gamma (-/-) mice that bound C. neoformans but did not ingest it retained the ability to ruffle in response to chemoattractants. These results imply that the inhibition of FKN- or CSF-1-stimulated cell ruffling was a direct consequence of the phagocytosis process. Since cell ruffling is a prelude to chemotaxis, this observation links two functions of macrophages that are critical to host defense, chemotaxis and phagocytosis. Phagocytosis-induced chemotactic suppression may enhance host defense by keeping these antimicrobial effector cells at infected sites and reduce the likelihood of microbial spread by wandering macrophages containing infectious cargo.

Polymorphonuclear function in naturally occurring renal failure in dogs

Chronic renal failure causes immunosuppression in people and is thought to be one of the causes of non-infectious secondary immunosuppression in dogs. The purpose of this study was to evaluate changes in counts and activity of polymorphonuclears in dogs with chronic renal failure in various stages. Haematological, biochemical examinations and examination of non-specific immune response cells (total and differential leukocyte counts, phagocytosis of methacrylate particles, chemiluminescence test, and level of lysozyme) were performed in blood samples obtained from these dogs. Neutrophilia, lymphopoenia and a decreased number of eosinophils in comparison with healthy control were the main findings in groups with clinical signs. We found the statistically highly significant elevation of lysozyme level; it was in a strong positive correlation with the level of urea, creatinine and phosphorus. We did not find any statistically significant changes in phagocytosis process and other serological factors. In conclusion, despite the reports from human medicine, chronic renal failure in dogs does not alter phagocytosis. From this aspect, the elevation of lysozyme level is the main effect of uraemia.