Strong Phagocytic Activity Research Articles

Suppression of Phagocytic Activity Leads to the Efficient Surface Modification of Macrophages with Liposomes for Developing a Biomimetic Drug Delivery System.

Macrophages selectively infiltrate the lesion sites of several diseases, including cancers, and, thus, have attracted attention as a biomimetic drug delivery carrier. To achieve the efficient drug loading of macrophages with minimal cytotoxicity, drugs are preferably encapsulated into nanoparticles, such as liposomes, and modified on the surface of macrophages rather than being incorporated into cells. However, liposomes are rapidly taken up by macrophages after binding to the cell surface because of their strong phagocytic activity. To overcome this, we herein attempted to modify the surface of macrophages with liposomes by suppressing their phagocytic activity using a pretreatment with anionic liposomes. We confirmed that 1,2-distearoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DSPG)- and cholesterol-rich anionic liposomes were efficiently taken up by RAW264.7 murine macrophage-like cells. Furthermore, the cellular uptake of anionic liposomes by RAW264.7 cells was higher in the absence of fetal bovine serum (FBS) than in its presence. Moreover, the viability of RAW264.7 cells was maintained above 90% when cells were incubated with anionic liposomes for 3 h, whereas viability was markedly decreased after a 24-h incubation. Based on these results, we pretreated RAW264.7 cells by an incubation with DSPG- and cholesterol-rich liposomes for 3 h in the absence of FBS. This pretreatment significantly inhibited the internalization of other liposomes, which subsequently bound to the cell surface. Therefore, we succeeded in modifying the surface of macrophages with liposomes, and liposome-modified macrophages have potential as a biomimetic active drug delivery carrier.

Immune defense mechanisms against a systemic bacterial infection in the cat flea (Ctenocephalides felis)

A significant amount of work has been devoted towards understanding the cellular and humoral immune responses in arthropod vectors. Although fleas (Siphonaptera) are vectors of numerous bacterial pathogens, few studies have examined how these insects defend themselves from infection. In this study, we investigated the immune defense mechanisms in the hemocoel of cat fleas (Ctenocephalides felis), currently the most important flea pest of humans and many domestic animals. Using model species of bacteria (Micrococcus luteus, Serratia marcescens, and Escherichia coli), we delivered a systemic infection and measured the following: antimicrobial activity of hemolymph, levels of free radicals resulting from the induction of oxidase-based pathways, number of circulating hemocytes, phagocytosis activity of circulating hemocytes, and in vivo bacteria killing efficiency when phagocytosis activity is limited. Our results show that the antimicrobial activity of flea hemolymph increases in response to certain species of bacteria; yet, a systemic infection with the same bacterial species did not influence levels of hydrogen peroxide (H2O2), a reactive intermediate of oxygen, at the same time. Additionally, the number of circulating hemocytes increases in response to E. coli infection, and these cells display strong phagocytic activity against this bacterium. Moreover, limiting phagocytosis by injecting polystyrene beads subsequently increases flea susceptibility to E. coli infection when compared to injury controls; however, impairing the cellular immune response itself did not increase flea susceptibility to infection when compared to untreated fleas. Overall, this work yields significant insight into how fleas interact with bacterial pathogens in their hemocoel, and suggests that cellular and humoral immune responses cooperate to combat systemic bacterial infections.

Establishment of a Coilia nasus Gonadal Somatic Cell Line Capable of Sperm Induction In Vitro.

Simple SummaryThe induced differentiation of sperm cells in vitro is a key technology for germplasm conservation. Coilia nasus is one of the “Three Delicious Species in the Yangtze River”, its germplasm resources have declined significantly over the past few decades. To protect the declining of Coilia nasus, a gonadal somatic cell line from fresh gonadal tissues (CnGSC) of adult Coilia nasus was isolated that can be cultured and proliferated in vitro for a long time. Co-culture of CnGSC with a medaka spermatogonial stem cell (SG3) line led to the induction of sperm in vitro. Further experiments showed that it is the lysate of CnGSC that induced the differentiation of SG3 in vitro. Our findings will help to further study the conservation of germplasm resources of endangered fishes with important values.Coilia nasus is an important economic anadromous migratory fish of the Yangtze River in China. In recent years, overfishing and the deterioration of the ecological environment almost led to the extinction of the wild resources of C.nasus. Thus, there is an urgent need to protect this endangered fish. Recently, cell lines derived from fish have proven a promising tool for studying important aspects of aquaculture. In this study, a stable C. nasus gonadal somatic cell line (CnCSC) was established and characterized. After over one year of cell culture (>80 passages), this cell line kept stable growth. RT-PCR results revealed that the CnGSC expressed some somatic cell markers such as clu, fshr, hsd3β, and sox9b instead of germ cell markers like dazl, piwi, and vasa. The strong phagocytic activity of CnGSC suggested that it contained a large number of Sertoli cells. Interestingly, CnGSC could induce medaka spermatogonial cells (SG3) to differentiate into elongated spermatids while co-cultured together. In conclusion, we established a C. nasus gonadal somatic cell line capable of sperm induction in vitro. This research provides scientific evidence for the long-term culture of a gonadal cell line from farmed fish, which would lay the foundation for exploring the regulatory mechanisms between germ cells and somatic cells in fish.

Gold Nanorods Induce Endoplasmic Reticulum Stress and Autocrine Inflammatory Activation in Human Neutrophils.

Gold nanorods (AuNRs) are promising agents for diverse biomedical applications such as drug and gene delivery, bioimaging, and cancer treatment. Upon in vivo application, AuNRs quickly interact with cells of the immune system. On the basis of their strong intrinsic phagocytic activity, polymorphonuclear neutrophils (PMNs) are specifically equipped for the uptake of particulate materials such as AuNRs. Therefore, understanding the interaction of AuNRs with PMNs is key for the development of safe and efficient therapeutic applications. In this study, we investigated the uptake, intracellular processing, and cell biological response induced by AuNRs in PMNs. We show that uptake of AuNRs mainly occurs via phagocytosis and macropinocytosis with rapid deposition of AuNRs in endosomes within 5 min. Within 60 min, AuNR uptake induced an unfolded protein response (UPR) along with induction of inositol-requiring enzyme 1 α (IREα) and features of endoplasmic reticulum (ER) stress. This early response was followed by a pro-inflammatory autocrine activation loop that involves LOX1 upregulation on the cell surface and increased secretion of IL8 and MMP9. Our study provides comprehensive mechanistic insight into the interaction of AuNRs with immune cells and suggests potential targets to limit the unwanted immunopathological activation of PMNs during application of AuNRs.

Microanalysis of Fish Ovarian Follicular Atresia: A Possible Synergic Action of Somatic and Immune Cells.

The present study describes in detail the morphological characteristics of the process of ovarian follicular atresia in Redbelly tilapia (Coptodon zillii) during the nonbreeding season using light and electron microscopy and immunohistochemistry. The follicular regression process was initiated with shrinkage and disintegration of the nuclear membrane of oocytes resulting in dispersing of chromatin within the ooplasm, followed by marked hyperplasia and hypertrophy of follicular and granulosa cells, which exhibited a strong phagocytic activity to engulf the liquefied yolk particles. Rodlet cells and granulocytes were recorded on the follicular wall and invaded the regressed follicles. Rodlet cells expressed a strong immunoreactivity to matrix metalloperoxidase (MMP-9) and α-smooth muscle actin, while neutrophils expressed a strong reactivity to Myeloperoxidase-3 (MPO). In the advanced stage of follicular atresia, the yolk was almost phagocytized and resorbed and the regressed follicle lost its integrity and appeared to be formed of a cellular mass of phagocytic cells. Transmission electron microscopy revealed the presence of neutrophils, eosinophils, and dendritic cells within the atretic follicle in between these phagocytic cells. Moreover, numerous lysosomes, granules, and phagosomes were observed within the cytoplasm of both phagocytic cells and granulocytes. Telocytes were also demonstrated within the highly thickened richly vascularized theca layer during the late stages of follicular atresia. Immunohistochemical staining for caspase-3 established the participation of apoptosis in the advanced stages of follicular regression. Immune cells, rodlet cells, and telocytes in combination with follicular cells play an essential role in follicular atresia. In conclusion, the present study provides a new evidence on the role of both somatic and immune cells in the phenomenon of ovarian follicular atresia in Redbelly tilapia (Coptodon zillii) during the nonbreeding season.

Genetically Modified Mouse Mesenchymal Stem Cells Expressing Non-Structural Proteins of Hepatitis C Virus Induce Effective Immune Response.

Hepatitis C virus (HCV) is one of the major causes of chronic liver disease and leads to cirrhosis and hepatocarcinoma. Despite extensive research, there is still no vaccine against HCV. In order to induce an immune response in DBA/2J mice against HCV, we obtained modified mouse mesenchymal stem cells (mMSCs) simultaneously expressing five nonstructural HCV proteins (NS3-NS5B). The innate immune response to mMSCs was higher than to DNA immunization, with plasmid encoding the same proteins, and to naïve unmodified MSCs. mMSCs triggered strong phagocytic activity, enhanced lymphocyte proliferation, and production of type I and II interferons. The adaptive immune response to mMSCs was also more pronounced than in the case of DNA immunization, as exemplified by a fourfold stronger stimulation of lymphocyte proliferation in response to HCV, a 2.6-fold higher rate of biosynthesis, and a 30-fold higher rate of secretion of IFN-γ, as well as by a 40-fold stronger production of IgG2a antibodies to viral proteins. The immunostimulatory effect of mMSCs was associated with pronounced IL-6 secretion and reduction in the population of myeloid derived suppressor cells (MDSCs). Thus, this is the first example that suggests the feasibility of using mMSCs for the development of an effective anti-HCV vaccine.

Application of CNTF or FGF-2 increases the number of M2-like macrophages after optic nerve injury in adult Rana pipiens.

We have previously shown that a single application of the growth factors ciliary neurotrophic factor (CNTF) or fibroblast growth factor 2 (FGF-2) to the crushed optic nerve of the frog, Rana pipiens, increases the numbers and elongation rate of regenerating retinal ganglion cell axons. Here we investigate the effects of these factors on the numbers and types of macrophages that invade the regeneration zone. In control PBS-treated nerves, many macrophages are present 100 μm distal to the crush site at 1 week after injury; their numbers halve by 2 weeks. A single application of CNTF at the time of injury triples the numbers of macrophages at 1 week, with this increase compared to control being maintained at 2 weeks. Application of FGF-2 is equally effective at 1 week, but the macrophage numbers have fallen to control levels at 2 weeks. Immunostaining with a pan-macrophage marker, ED1, and a marker for M2-like macrophages, Arg-1, showed that the proportion of the putative M2 phenotype remained at approximately 80% with all treatments. Electron microscopy of the macrophages at 1 week shows strong phagocytic activity with all treatments, with many vacuoles containing axon fragments and membrane debris. At 2 weeks with PBS or FGF-2 treatment the remaining macrophages are less phagocytically active, containing mainly lipid inclusions. With CNTF treatment, at 2 weeks many of the more numerous macrophages are still phagocytosing axonal debris, although they also contain lipid inclusions. We conclude that the increase in macrophage influx seen after growth factor application is beneficial for the regenerating axons, probably due to more extensive removal of degenerating distal axons, but also perhaps to secretion of growth-promoting substances.

Optimization of macrophage isolation from the Persian sturgeon and the Caspian kutum fish: a comparative study.

The aim of this research was a comparative study on the isolation and culture of head kidney macrophages derived from Acipenser persicous and Rutilus frisii kutum as teleost and chondrostei species of fish. The macrophages were isolated by density gradient sedimentation, followed by adherence to a plastic surface. They exhibited strong phagocytic activity against bacteria. The effect of cell density, incubation time, FBS percentage, pH and temperatures on the cell number and viability were determined and compared. Also, the effect of light/dark regimen on viability, adherence, release of reactive oxygen species (ROS) and nitric oxide (NO) in the macrophages was determined. The results showed that the Caspian kutum macrophages were more sensitive to FBS percentage and cell density whereas the Persian sturgeon macrophages were more sensitive to pH of the cell culture media. The adherence and viability of the macrophages from both fish species firstly increased (P < 0.05) after exposure to a light/dark regimen, but then significantly decreased as did ROS and NO productions. For the first time, this study has determined the optimal conditions for primary culture of macrophages derived from sturgeons, and shows the unique effect of light on the biology of fish immune cells.

The characteristics of vessel lining cells in normal spleens and their role in the pathobiology of myelofibrosis

AbstractThe CD34−CD8α+, sinusoid lining, littoral cells (LCs), and CD34+CD8α−, splenic vascular endothelial cells (SVECs) represent 2 distinct cellular types that line the vessels within normal spleens and those of patients with myelofibrosis (MF). To further understand the respective roles of LCs and SVECs, each was purified from normal and MF spleens, cultured, and characterized. Gene expression profiling indicated that LCs were a specialized type of SVEC. LCs possessed a distinct gene expression profile associated with cytoskeleton regulation, cellular interactions, endocytosis, and iron transport. LCs also were characterized by strong phagocytic activity, less robust tube-forming capacity and a limited proliferative potential. These characteristics underlie the role of LCs as cellular filters and scavengers. Although normal LCs and SVECs produced overlapping as well as distinct hematopoietic factors and adhesion molecules, the gene expression profile of MF LCs and SVECs distinguished them from their normal counterparts. MF SVECs were characterized by activated interferon signaling and cell cycle progression pathways and increased vascular endothelial growth factor receptor, angiopoietin-2, stem cell factor, interleukin (IL)-33, Notch ligands, and IL-15 transcripts. In contrast, the transcription profile of MF LCs was associated with mitochondrial dysfunction, reduced energy production, protein biosynthesis, and catabolism. Normal SVECs formed in vitro confluent cell layers that supported MF hematopoietic colony formation to a greater extent than normal colony formation. These data provide an explanation for the reduced density of LCs observed within MF spleens and indicate the role of SVECs in the development of extramedullary hematopoiesis in MF.

Enterotoxigenic Escherichia coli is phagocytosed by macrophages underlying villus-like intestinal epithelial cells: modeling ex vivo innate immune defenses of the human gut

ABSTRACTThere is a paucity of information on diarrheagenic enterotoxigenic Escherichia coli (ETEC)’s interaction with innate immune cells, in part due to the lack of reliable models that recapitulate infection in human gut. In a recent publication, we described the development of an ex vivo enteroid-macrophage co-culture model using human primary cells. We reported that macrophages residing underneath the epithelial monolayer acquired “resident macrophage” phenotype characterized by lower production of inflammatory cytokines and strong phagocytic activity. These macrophages extended projections across the epithelium, which captured ETEC applied to the apical side of the epithelium and reduced luminal bacterial load. Additional evidence presented in this addendum confirms these findings and further demonstrates that macrophage adaptation occurs regardless of the stage of differentiation of epithelial cells, and that ETEC uptake arises rapidly after infection. The enteroid-macrophage co-culture represents a novel and relevant tool to study host-cell interactions and pathogenesis of enteric infections in humans.

A New Method to Isolate and Culture Rat Kupffer Cells

BackgroundPrevious methods for Kupffer cells (KCs) isolation require sophisticated skills and tedious procedures. Few studies have attempted to explore the self-renewal capacity of KCs in vitro. Therefore, the aim of this study was to establish a simple method for rat KCs isolation and further investigate the mitotic potential of KCs in vitro.MethodsKCs were obtained by performing one-step perfusion, enzymatic tissue treatment, differential centrifugation and selective adherence. The proliferation ability of cultured KCs was determined by MTT assay and Propidium Iodide FACS analysis. Phagocytic assay and ED-1, ED-2 immunofluorescence were used to identify cell phenotype. After stimulation with LPS, the expression of surface antigens (MHCII, CD40, CD80, and CD86) and the production of cytokines (NF-κB, TNF-α, IL-6 and IL-10) were measured for cell function identification.ResultsKCs were isolated with certain numbers and reasonable purities. The KCs were able to survive until at least passage 5 (P5), and at P3 showed equally strong phagocytic activity as primary KCs (P0). After stimulation with LPS, the change in the expression of surface antigens and the production of cytokines for P3 cells was similar to that for P0 cells.ConclusionsOur study provides a simple and efficient method for KCs isolation, and reveals that self-renewing KCs have the same phagocytic activity and functions as primary KCs.

Peyer's Patch Dendritic Cells Sample Antigens by Extending Dendrites Through M Cell-Specific Transcellular Pores

Peyer's patches (PPs) of the small intestine are antigen sampling and inductive sites that help establish mucosal immunity. Luminal antigens are transported from the mucosal surface of PPs to the subepithelial dome (SED), through the specialized epithelial M cells of the follicle-associated epithelium. Among the SED resident dendritic cells (DCs), which are situated ideally for taking up these antigens, some express high levels of lysozyme (LysoDC) and have strong phagocytic activity. We investigated the mechanisms by which LysoDCs capture luminal antigens in vivo. We performed 2-photon microscopy on explants of PPs from mice in which the enhanced green fluorescent protein gene was inserted into the lysozyme M locus (lys-EGFP mice), allowing fluorescence detection of LysoDC. LysoDC extended dendrites through M-cell-specific transcellular pores to the gut lumen. The M-cell adhesion molecules junctional adhesion molecule-A and epithelial cell adhesion molecule were recruited to sites of transcellular migration. Transcellular dendrites scanned the M-cell apical surface and the gut luminal content; they were able to take pathogenic bacteria and inert particles in the lumen before retracting back to the SED. We describe an antigen sampling mechanism that occurs in PPs and involves cooperation between M cells of the follicle-associated epithelium and DCs of the subepithelial dome. This process might be developed to target vaccines to the mucosa.

Dimeric Transferrin Inhibits Phagocytosis of Residual Bodies by Testicular Rat Sertoli Cells1

Transferrin is well known as an iron transport glycoprotein. Dimeric or tetrameric transferrin forms have recently been reported to modulate phagocytosis by human leukocytes. It is mainly synthesized by the liver, and also by other sources, such as Sertoli cells of the testis. Sertoli cells show a strong phagocytic activity toward apoptotic germ cells and residual bodies. Here, we provide evidence that purified human dimeric transferrin from commercial sources decreased residual body phagocytosis, unlike monomeric transferrin. The presence of iron appeared essential for dimeric transferrin inhibitory activity. Importantly, dimeric transferrin could be visualized by immunoblotting in Sertoli cell lysates as well as in culture media, indicating that dimeric transferrin could be physiologically secreted by Sertoli cells. By siRNA-mediated knockdown, we show that endogenous transferrin significantly inhibited residual body ingestion by Sertoli cells. These results are the first to identify dimeric transferrin in Sertoli cells and to demonstrate its implication as a physiological modulator of residual body phagocytosis by Sertoli cells.

Phagocytosis of O4+ axonal fragments in vitro by p75− neonatal rat olfactory ensheathing cells

Olfactory ensheathing cells (OECs) have gained wide interest because of their unique regeneration-promoting capacity. However, despite their frequent use in regeneration studies, the characterization of the cells has remained fragmentary. In the present study, we analyzed freshly dissociated neonatal rat OECs at the light and electron microscopic level and studied their fate in vitro using a novel two-step labeling protocol based on antibody internalization. We report the identification and characterization of two distinct OEC populations in situ and in primary cell suspensions that differed in number, p75 NGF receptor expression, and O4 immunoreactivity. The major OEC population in primary cells suspensions did not express p75 but stained positive for the glycolipid O4 (p75-/O4+). During culturing, these cells upregulated p75 expression and lost O4 immunoreactivity. Conversely, the minor OEC population consisted of p75+/O4- OECs that maintained p75 expression in vitro. Interestingly, ultrastructural analysis revealed not only that O4 immunoreactivity of p75- OECs was, in fact, due to O4+ axonal fragments adhering to the cell surface but also that p75- OECs rapidly phagocytosed these fragments in vitro. Taken together, the identification of two distinct OEC populations in the neonatal olfactory bulb that converge into single p75+ phenotype in vitro is reported. The observation that upregulation of p75 receptor expression in vitro was only apparent in those OECs closely associated with O4+ axonal processes may suggest that axonal signalling in vivo negatively regulates p75 receptor expression. The strong phagocytic activity of OECs in vitro may reflect one important aspect of their physiological function.

Development of CD4+ Macrophages from Intrathymic T Cell Progenitors Is Induced by Thymic Epithelial Cells

It was recently demonstrated that there are CD4(+) macrophages, which exhibit strong phagocytic activity, in the thymus. They are suggested to play an important role for the elimination of apoptotic thymocytes. However, the origin and nature of CD4(+) macrophages in the thymus remain unexplored. In this study, we describe that the most immature intrathymic progenitors (CD25(-)/CD44(+)/FcR(+)) give rise to CD4(+) macrophages by oncostatin M-responsive thymic epithelial cells (ORTEC) in an IL-7-dependent manner. Neither conditioned medium of ORTEC nor a mixture of cytokines induced CD4(+) macrophages, and oncostatin M receptor was not expressed in thymocytes, suggesting that the development of CD4(+) macrophages from the immature thymocytes requires a direct interaction with ORTEC. These results collectively suggest that the development of CD4(+) macrophages from the intrathymic T cell progenitors is induced by thymic epithelial cells.

A role for ezrin in a neglected metastatic tumor function

In the previous issue of Trends in Molecular Medicine, Kent Hunter discussed the potential effects of ezrin in tumormetastasis [1]. In his article, two recent papers were described, which identified ezrin as a key component in the metastasis of pediatric tumors [2,3]. The speculation concerning the role of ezrin in tumor metastasis was based on both the best-known ezrin functions and the ability of ezrin to confer metastatic capabilities to lowmetastatic tumors in experimental models. However, the most recognized ezrin function is to connect membrane proteins to the actin cytoskeleton [4–6], whereas the tumor functions that are directly related to metastatic behaviour are the capacity of tumor cells to migrate within tissues, transmigrate through vessels and to adhere to the metastatic organs. Therefore, the linkage between ezrin and metastatic behaviour is through the adhesion molecules that are known to depend on the ezrin-mediated linkage to actin, such as CD44, and are directly related to the invasion and metastasis of tumors [7]. However, in a recent paper, another ezrin-mediated function that might influence metastatic behaviour, which is related to a neglected tumor activity, has been proposed [8]. The phagocyte-like behavior of tumor cells was first observed a century ago [9,10]. Numerous studies have since described the phagocytic activity of various murine and human tumor cells against dead cells and undefined particles [11,12]. However, oncologists have generally considered the finding of phagocytosed nuclei, cell debris and matrix components within tumor cells a curiosity and the result of an aberrant or an inefficient activity within themalignant cell. Using several quantitativemeasures of phagocytic activity in tumor cell lines that were derived from either metastatic lesions or primary tumors, it was reported that cell lines derived exclusively frommetastatic tumors showed strong phagocytic activity. On the basis of previous evidence on the essential role of ezrin in the phagocytic process ofmacrophages [13], the role of ezrin on the phagocytic activity of human tumor cells was examined. This data showed that ezrin is localized within the phagocytic vacuoles (Figure 1), together with lysosomal antigens [8]. Furthermore, by using oligo-antisense inhibition to block the synthesis of ezrin, the phagocytic activity of metastatic tumor cells was abrogated. However, the ezrin levels were comparable in both metastatic and non-metastatic tumors, suggesting that the overexpression of ezrin was not the sole cause of this phenomenon. In fact, contrasting results on the level of ezrin in adult tumors have been reported [14,15]. Therefore, it appears that a mechanism that is involved in ezrin activation and phosphorylation becomes deregulated in tumor cells, particularly in adult tumors. Rho-GTPases, which are known to be involved in ezrin–radixin–moesin (ERM) activation, are good candidates for the aberrant isoforms that are overexpressed in tumor metastasis [16], and Rho activation might induce aberrant phagocytic activity in non-professional phagocytes [17]. The role of phagocytic activity of tumors in metastasis needs to be clarified. Two major hypotheses can be proposed: (i) the ability of tumors to phagocytose might contribute to tumor escape from immune surveillance through the subtraction of antigenic material that is required for the processing activity of professional antigen-presenting cells, or (ii) a more complex hypothesis, in which the phagocytic activity allows tumors to survive in adverse environments, such as those that occur during hypoxic conditions because of the low blood supply during tumor growth or in metastatic organs, by ‘feeding’ on apoptotic cells and/or extracellular matrix components.

Factors influencing phagocytic response of macrophages from the sea bass Dicentrarchus labrax L.): An ultrastructural and quantitative study

Background Although phagocytosis is considered the main nonspecific defense mechanism in fish, the significance of the influence of bacterial properties and assay conditions on this mechanism has not been established. We report the influence of leukocyte source, bacterial species, presence or absence of a bacterial wall, bacterial status (live or dead), and bacterial opsonization on in vitro phagocytosis by sea bass (Dicentrarchus labrax L.) macrophages. Methods Leukocytes were challenged with bacteria under different conditions and ultrastructurally studied. The number of phagocytic macrophages and the number of bacteria ingested per macrophage were quantified by microscopical counting, and the data obtained were statistically analyzed following general linear models. Results Macrophages from sea bass peritoneal exudate showed a greater capacity to engulf bacteria than did those isolated from blood, which, in turn, had greater engulfment properties than did those isolated from head-kidney. Greater phagocytic activity was observed in the assays carried out with Escherichia coli than in those carried out with Salmonella typhimurium, especially when the TA1950 S. typhimurium strain (with wall) was used. Macrophages showed greater phagocytic activity against live bacteria. Bacterial opsonization had a variable effect on phagocytosis. Sea bass macrophages did not always ingest the same number of bacteria. Conclusions Sea bass macrophages have strong bacterial phagocytic activity. Significant differences were found that had been influenced by bacterial properties as well as by assay conditions. Positive correlation between the number of phagocytic macrophages and the number of bacteria ingested per phagocyte was observed. Anat. Rec. 248:533-541, 1997. © 1997 Wiley-Liss, Inc.

Factors influencing phagocytic response of macrophages from the sea bass (Dicentrarchus labrax L.): an ultrastructural and quantitative study.

Although phagocytosis is considered the main nonspecific defense mechanism in fish, the significance of the influence of bacterial properties and assay conditions on this mechanism has not been established. We report the influence of leukocyte source, bacterial species, presence or absence of a bacterial wall, bacterial status (live or dead), and bacterial opsonization on in vitro phagocytosis by sea bass (Dicentrarchus labrax L.) macrophages. Leukocytes were challenged with bacteria under different conditions and ultrastructurally studied. The number of phagocytic macrophages and the number of bacteria ingested per macrophage were quantified by microscopical counting, and the data obtained were statistically analyzed following general linear models. Macrophages from sea bass peritoneal exudate showed a greater capacity to engulf bacteria than did those isolated from blood, which, in turn, had greater engulfment properties than did those isolated from head-kidney. Greater phagocytic activity was observed in the assays carried out with Escherichia coli than in those carried out with Salmonella typhimurium, especially when the TA1950 S. typhimurium strain (with wall) was used. Macrophages showed greater phagocytic activity against live bacteria. Bacterial opsonization had a variable effect on phagocytosis. Sea bass macrophages did not always ingest the same number of bacteria. Sea bass macrophages have strong bacterial phagocytic activity. Significant differences were found that had been influenced by bacterial properties as well as by assay conditions. Positive correlation between the number of phagocytic macrophages and the number of bacteria ingested per phagocyte was observed.

Establishment and Characterization of an Epstein-Barr Virus Transformed Cell Line With Strong Phagocytic Activity

AbstractAn immunoglobulin M (IgM)-positive cell line, Ms 28, apparently spontaneously transformed by Epstein-Barr virus (EBV) was established from peripheral blood cells of a patient with immature myeloblastic leukemia. It has been characterized according to phenotype, cytochemistry, and membrane antigen pattern. The cell line expresses lymphoid markers like CD 19, CD 22, and CD 30 and synthesizes and secretes IgM. Monocyte markers CD 11c, CD 14, and CD 15 are absent. Neither interleukin-1 (IL-1), nor tumor necrosis factor (TNF-α) are produced. But Ms 28 cells show strong phagocytic activity and engulf Latex particles and sheep RBCs (SRBCs) that need not to be opsonized. The phagocytic activity can be inhibited by chloroquine. Both phagocytosis and EBV nuclearantigen (EBNA) expression can be observed in one and the same cell. Ms 28 cells might be useful to study immunologic activities like antigen processing and presentation.

Establishment and characterization of an Epstein-Barr virus transformed cell line with strong phagocytic activity

An immunoglobulin M (IgM)-positive cell line, Ms 28, apparently spontaneously transformed by Epstein-Barr virus (EBV) was established from peripheral blood cells of a patient with immature myeloblastic leukemia. It has been characterized according to phenotype, cytochemistry, and membrane antigen pattern. The cell line expresses lymphoid markers like CD 19, CD 22, and CD 30 and synthesizes and secretes IgM. Monocyte markers CD 11c, CD 14, and CD 15 are absent. Neither interleukin-1 (IL-1), nor tumor necrosis factor (TNF-alpha) are produced. But Ms 28 cells show strong phagocytic activity and engulf Latex particles and sheep RBCs (SRBCs) that need not to be opsonized. The phagocytic activity can be inhibited by chloroquine. Both phagocytosis and EBV nuclear-antigen (EBNA) expression can be observed in one and the same cell. Ms 28 cells might be useful to study immunologic activities like antigen processing and presentation.