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PubMed1987

Role of the alveolar macrophage in host defense and immunity to Legionella micdadei pneumonia in the guinea pig.

Guinea pigs develop a lethal pneumonia after intratracheal infection with Legionella micdadei, and the lung displays pathological changes similar to those observed in humans. To investigate the role of the resident alveolar macrophage in the pathogenesis of L. micdadei pneumonia, guinea pig alveolar macrophages obtained by bronchoalveolar lavage were cultured in vitro and infected with L. micdadei. In the absence of opsonins L. micdadei was phagocytized by, and multiplied within, alveolar macrophages with greater than a 100-fold increase in cell-associated colony forming units over 20 h. L. micdadei opsonized with complement or antibody multiplied within alveolar macrophages at the same rate as unopsonized bacteria. Guinea pigs which were treated with antimicrobials after infection with L. micdadei and recovered from the pneumonia were immune to challenge with an otherwise lethal inoculum of L. micdadei. However, the growth curve of both unopsonized and opsonized L. micdadei in the alveolar macrophages from immune animals was essentially identical to that in macrophages from susceptible animals. Thus, the resident alveolar macrophage is not capable of limiting the growth of Legionella. Rather, the alveolar macrophages appear to be the primary site of Legionella multiplication within the lung. Although alveolar macrophages may participate in other aspects of pulmonary immunity to the legionellae, these data indicate that the alveolar macrophage alone does not act as an effector cell in cell-mediated immunity to Legionella.

Animals↗
PubMed1989

Modulation of bovine neutrophil antibacterial activities by Pasteurella haemolytica A1 purified capsular polysaccharide.

Preincubation of bovine neutrophils with Pasteurella haemolytica A1 purified capsular polysaccharide markedly diminished their ability to ingest and kill P. haemolytica, but not Escherichia coli, in vitro. Ingestion and killing were impaired even when the P. haemolytica were preopsonized, thus suggesting that the inhibitory effects of the polysaccharide included a direct effect on bovine neutrophils rather than simply competition for serum opsonins. Preincubation of neutrophils with purified polysaccharide did not elicit a chemiluminescence response, nor did it alter the chemiluminescence response of neutrophils to subsequent stimulation with opsonized P. haemolytica or opsonized zymosan. In addition, purified polysaccharide alone was neither chemotactic nor did it induce a shape change in bovine neutrophils. These data suggest that the deposition of capsular polysaccharide in the lung during the onset of pulmonary pasteurellosis might impair the ability of neutrophils to ingest and kill P. haemolytica. The capsular polysaccharide of P. haemolytica, therefore, may contribute in part to the fibrinous pleuropneumonia that characterizes acute pasteurellosis.

Animals↗
PubMed2006

Purification of properoxinectin, a myeloperoxidase homologue and its activation to a cell adhesion molecule.

Peroxidases are important mediators of innate immune reactions throughout the animal kingdom. In many arthropods a myeloperoxidase homologue, peroxinectin, is known to function as a cell adhesion factor and an opsonin. Here, we report in the freshwater crayfish Pacifastacus leniusculus the isolation of properoxinectin, inactive in cell adhesion, and we also show that properoxinectin is produced in the mature blood cells whereas the hematopoietic tissue contains very little of this protein. Both properoxinectin and peroxinectin are catalytically active as peroxidases, at least when using low molecular weight substrates. The extracellular processing of properoxinectin into an active cell adhesion protein was found to involve proteolytic steps shared with the prophenoloxidase activating system to yield catalytically active phenoloxidase. Thus, the regulation of activities by two ancient metalloproteins, both potentially producing highly toxic substances aimed at pathogens, is carried out by limited proteolysis. The proteolytic processing is triggered in the presence of microbial compounds such as beta-glucans or lipopolysaccharide after the release of properoxinectin and prophenoloxidase activating serine proteinases from the blood cells.

Amino Acid Sequence↗
PubMed2005

Isolation of mannose-binding C-type lectin from Heliothis virescens pupae.

A mannose-binding C-type lectin (MBL) was isolated by affinity chromatography from Heliothis virescens immune pupal hemolymph. The immune pupal hemolymph was obtained after bacterial injection of live Enterobacter cloacae bacteria. MBL in mammals acts as an opsonin for phagocytosis and activates the lectin complement pathway of the innate immune response, which leads to killing of gram-negative bacteria and enveloped viruses. The affinity-purified and reduced pupal MBL showed a single band of 36 kDa by SDS-PAGE (12% gel). A dot-immunoblot ELISA (using guinea pig anti-MBL IgG as primary antibody) demonstrated specificity of the antibody for the affinity-purified pupal MBL. The immune pupal hemolymph contained 21 microg of MBL per ml of hemolymph. The amino acid composition of the purified pupal MBL was determined with high amounts of arginine and histidine detected. The presence of MBL in insect pupae has not before been reported and could be important in pupal innate immunity to bacterial infection.

Amino Acid Sequence↗
PubMed2006

Characterization of an equine mannose-binding lectin and its roles in disease.

The mannose-binding lectin (MBL), a pattern recognition serum protein, participates in the innate immune system of mammals as an opsonin. In humans, MBL plays a key role in first-line host defense against infection during the lag period prior to the development of a specific immune response. MBL also activates complement via the lectin pathway that requires a MBL-associated serine protease-2 (MASP-2). Homologues of human MBL (hMBL) have been identified in a variety of mammals, fish, and primitive animals such as ascidians. In this study, we report that equine MBL (eMBL) has properties that are similar to hMBL. In addition, we found low levels of MBL:MASP activity in sick horses compared to healthy horses. These results suggest that eMBL is involved in the immune response of the horse and that low MBL:MASP activity could be used to monitor immune function and clinical outcome.

Amino Acid Sequence↗
PubMed2007

Psidin is required in Drosophila blood cells for both phagocytic degradation and immune activation of the fat body.

Phagocytic blood cells are critical to innate immune defense: They internalize and destroy microbial invaders and produce signals that trigger other immune responses. Despite this central role, the in vivo contributions of phagocytosis to systemic immune activation are not well understood. Drosophila has proven a fruitful model for the investigation of evolutionarily conserved innate immune mechanisms, including NF-kappaB-dependent transcriptional induction, RNAi in antiviral responses, and phagocytosis. The phagocytes of Drosophila encounter bacterial invaders early in infection and contribute to survival of infection. Phagocytosis in flies and mammals is highly homologous: Both rely on scavenger receptors, opsonins, and actin rearrangements for engulfment; have phagosomal cysteine proteases active at low pH; and can be subverted by similar intracellular pathogens. Although the role of Drosophila phagocytes in the activation of other immune tissues has not been clear, we show that induction of the antibacterial-peptide gene Defensin in the fat body during infection requires blood-cell contributions. We identify a gene, psidin, that encodes a lysosomal protein required in the blood cells for both degradation of engulfed bacteria and activation of fat-body Defensin. These data establish a role for the phagocytic blood cells of Drosophila in detection of infection and activation of the humoral immune response.

Animals↗
PubMed2004

An immunohistochemical study on complement component C3 in juvenile Atlantic halibut (Hippoglossus hippoglossus L.).

The complement systems of fish are well developed and play an important role in the immune response. Complement C3 is the central protein of all three activation pathways, being the major opsonin of the complement system and essential for the generation of the membrane attack complex. Very little is known about the development of the complement system in fish. In this study, we detect the presence of C3 in halibut larvae from the age of 37 degrees d post hatching until 1050 degrees d (i.e. 5-99 d post hatching) using immunohistochemistry with specific antibodies produced against the beta-chain of halibut C3. At the different stages of larval maturation, C3 was detectable in yolksac, muscle, liver, brain, chondrocytes, spinal chord, eye, heart, stomach, intestines, oesophagus, pharynx and kidney. Our findings suggest a role of complement in the formation and generation of different organs, besides its important functions in the immune defence against invading pathogens.

Animals↗
PubMed2005

Hemocytes from the tobacco hornworm Manduca sexta have distinct functions in phagocytosis of foreign particles and self dead cells.

Phagocytosis is an important innate immune response against microbial infections and an effective mechanism to eliminate apoptotic cells. In vertebrates, phagocytes such as macrophages and dendritic cells are involved in phagocytosis. We demonstrate here that insect hemocytes have distinct functions in phagocytosis of foreign particles and self dead cells. Plasmatocytes from the tobacco hornworm Manduca sexta were major hemocytes involved in phagocytosis of non-self microsphere beads, whereas granulocytes were apparently the only hemocytes that phagocytose self dead cells. We also showed that M. sexta immulectin-2, a pattern recognition receptor that protects larvae from bacterial infection, has an opsonic activity in phagocytosis. Immulectin-2 bound to the surface of granulocytes from the naïve larvae, but more immulectin-2 bound to plasmatocytes when larvae were injected with microsphere beads. Coupling of immulectin-2 onto microsphere beads enhanced in vitro phagocytosis of the beads. Our results suggest that insect hemocytes can have specialized functions similar to vertebrate phagocytes in phagocytosis, and pattern recognition receptors may function as opsonins to enhance phagocytosis.

Animals↗
PubMed2005

Purification, characterization and cDNA cloning of a novel lipopolysaccharide-binding lectin from the shrimp Penaeus monodon.

In invertebrates, C-type lectin plays an important role in innate immunity by mediating the recognition of pathogens to host cells and clearing microinvaders. A few C-type lectins have been identified from shrimps, but none of their gene or protein sequences is known to date. In this paper, a C-type lectin (named PmLec) specific for bacterial lipopolysaccharide was purified from the serum of the shrimp Penaeus monodon. The binding of PmLec to lipopolysaccharide was mainly mediated through the O-antigen. PmLec had a strong hemagglutinating and bacterial-agglutinating activity as well as an opsonic effect that enhances hemocyte phagocytosis. The PmLec cDNA sequence was obtained from the cDNA library of P. monodon by polymerase chain reaction with the degenerated primer designed according to the amino-terminal residue sequence of purified PmLec. A 546-bp open reading frame was found to encode a putative protein comprising 182 amino acids and containing a preceding signal peptide of 17 amino acids. A C-type lectin domain existed in PmLec, but no glycosylation site was found. The recombinant PmLec protein expressed in Escherichia coli also showed the same agglutinating activity and opsonic effect as that of the native protein. This is the first report of a lectin cDNA from the shrimp. PmLec functions as a pattern-recognition protein and an opsonin in the shrimp, and it provides a clue to elucidate the role of lectin in the innate immunity of aquatic invertebrates at the molecular level.

Animals↗
PubMed2005

Selective granulocyte and monocyte apheresis as a new adjunct to enhance the efficacy of interferon-alpha + ribavirin in patients with high plasma hepatitis C virus.

BACKGROUND AND AIM: Selective granulocyte and monocyte/macrophage adsorptive apheresis is to increase the turnover of infected leucocytes and has increased CD4+ T cells, which are necessary for actions of interferon-alpha on hepatitis C virus. Therefore, granulocyte and monocyte apheresis was to enhance the efficacy of interferon + ribavirin. METHODS: Fifteen patients, 12 had interferon resistant hepatitis C virus and 3 were interferon naive. Hepatitis C virus genotype was 1b in 11 and 2a in 4. The mean plasma HCV-RNA was 728.3 kU/mL and alanine aminotransferase was 107.5 U/L. Granulocyte and monocyte apheresis was with the Adacolumn, which contains carriers that adsorb granulocytes and monocytes/macrophages. After five consecutive granulocyte and monocyte apheresis sessions over 5 days, interferon daily 6 million units for 4 weeks, then three times/week for 20 weeks+ribavirin (600-800 mg per patient per day) were given and followed for another 24 weeks. RESULTS: During granulocyte and monocyte apheresis, plasma HCV-RNA transiently fell by up to 55%. Similarly, incubation of blood with the Adacolumn carriers caused a significant fall in HCV-RNA. Four patients were unavailable for efficacy evaluation. In the other 11, alanine aminotransferase normalised and at 11 weeks, plasma HCV-RNA was negative; six of these (55%) maintained their remission during the follow up. CONCLUSION: Granulocyte and monocyte apheresis appears to deplete extra-hepatic hepatitis C virus reservoirs and generate active complement opsonins, which contribute to hepatitis C virus killing. Additional mechanism(s) are also likely and need to be elucidated in future studies with larger cohort of patients.

Adjuvants, Immunologic↗
PubMed2004

Antibody response to Candida albicans cell wall antigens.

The cell wall of Candida albicans is not only the structure where many essential biological functions reside but is also a significant source of candidal antigens. The major cell wall components that elicit a response from the host immune system are proteins and glycoproteins, the latter being predominantly mannoproteins. Both carbohydrate and protein moieties are able to trigger immune responses. Proteins and glycoproteins exposed at the most external layers of the wall structure are involved in several types of interactions of fungal cells with the exocellular environment. Thus, coating of fungal cells with host antibodies has the potential to profoundly influence the host-parasite interaction by affecting antibody-mediated functions such as opsonin-enhanced phagocytosis and blocking the binding activity of fungal adhesins to host ligands. In this review we examine various members of the protein and glycoprotein fraction of the C. albicans cell wall that elicit an antibody response in vivo. Some of the studies demonstrate that certain cell wall antigens and anti-cell wall antibodies may be the basis for developing specific and sensitive serologic tests for the diagnosis of candidiasis, particularly the disseminated form. In addition, recent studies have focused on the potential of antibodies against the cell wall protein determinants in protecting the host against infection. Hence, a better understanding of the humoral response triggered by the cell wall antigens of C. albicans may provide the basis for the development of (i) effective procedures for the serodiagnosis of disseminated candidiasis, and (ii) novel prophylactic (vaccination) and therapeutic strategies to control this type of infections.

Antibodies, Fungal↗
PubMed2006

Innate immunity of fish (overview).

The innate immune system is the only defence weapon of invertebrates and a fundamental defence mechanism of fish. The innate system also plays an instructive role in the acquired immune response and homeostasis and is therefore equally important in higher vertebrates. The innate system's recognition of non-self and danger signals is served by a limited number of germ-line encoded pattern recognition receptors/proteins, which recognise pathogen associated molecular patterns like bacterial and fungal glycoproteins and lipopolysaccharides and intracellular components released through injury or infection. The innate immune system is divided into physical barriers, cellular and humoral components. Humoral parameters include growth inhibitors, various lytic enzymes and components of the complement pathways, agglutinins and precipitins (opsonins, primarily lectins), natural antibodies, cytokines, chemokines and antibacterial peptides. Several external and internal factors can influence the activity of innate immune parameters. Temperature changes, handling and crowding stress can have suppressive effects on innate parameters, whereas several food additives and immunostimulants can enhance different innate factors. There is limited data available about the ontogenic development of the innate immunological system in fish. Active phagocytes, complement components and enzyme activity, like lysozyme and cathepsins, are present early in the development, before or soon after hatching.

Animals↗
PubMed2006

Complement component C3 transcription in Atlantic halibut (Hippoglossus hippoglossus L.) larvae.

The complement systems of fish are well developed and play an important role in the innate immune response. Complement C3 is the central protein of all three activation pathways and is the major opsonin of the complement system and essential for the generation of the membrane attack complex. A 1548 bp part of complement component C3 was isolated from a halibut liver cDNA library by immunoscreening. The deduced amino acid sequence showed that this part of halibut C3 contained key amino acids for factor H, I and properdin binding as well as two N-glycosylation sites. Digoxigenine labelled mRNA probes were synthesised and the transcription of C3 was monitored in three larval stages at 206, 430 and 1000 degrees d (30, 50 and 99 days post hatching), by in situ hybridisation. C3 mRNA was detected in muscle, liver, brain, chondrocytes, spinal cord, eye, intestines, oesophagus and kidney. These findings are in accordance with a former immunohistochemical study on halibut C3 protein ontogeny, indicating that C3 is indeed locally expressed in many organs from the youngest stages on. Complement may thus be linked to the formation and generation of different organs during development and play an important role in the early immune response of halibut larvae.

Amino Acid Sequence↗
PubMed2006

Respiratory burst activity of Atlantic cod (Gadus morhua L.) blood phagocytes differs markedly from that of rainbow trout.

In the present study we investigated the respiratory burst (RB) activity of Atlantic cod (Gadus morhua L.) blood phagocytes and we evaluated how the RB activity of cod blood cells differ from that of trout. The RB activities were measured directly from highly diluted whole blood as luminol-amplified chemiluminescence (CL) under various conditions. Studies regarding the blood dilutions for cod whole blood chemiluminescence measurements (WBCL) revealed that at a final blood dilution of 1.5 microl ml(-1) or less the CL response was strictly proportional to the number of phagocytes. This range of blood dilution did not markedly differ from that of trout. However, the opsonisation capacity of cod plasma was markedly poorer. The RB activity of phagocytes was most active at 15 degrees C when heterologous cod serum was used as a source of opsonin, whereas at final blood dilution of 8.0 microl ml(-1) (when homologous cod plasma was at a higher concentration) the highest RB activity was observed at 10 degrees C. Aeromonas salmonicida strain MT004 (As MT004) induced higher RB activity than the two known pathogens for cod, atypical A. salmonicida and Vibrio anguillarum. Cod blood phagocytes were more responsive to plastic surfaces and the adhesion response of phagocytes was partly inhibited but did not totally vanish even at a final gelatin concentration of 0.4%. Moreover, cod serum enhanced the adherence of phagocytes and cod blood phagocytes also showed slow spontaneous degranulation. Finally, within the tested anticoagulants (heparin, Na-citrate, EDTA) heparin treated blood phagocytes generated the highest RB activity.

Aeromonas salmonicida↗
PubMed2006

Molecular cloning and characterisation of two homologues of Mannose-Binding Lectin in rainbow trout.

Mannose-binding lectin (MBL) is a C-type lectin which participates in the innate immune system as an activator of the complement system and as opsonin after binding to certain carbohydrate structures on microorganisms and pathogens. C-type lectins are all Ca(2+)-dependent molecules and they share a tightly folded carbohydrate recognition domain (CRD). In this report the isolation and characterisation of cDNA transcripts encoding two mannose-binding lectin isoforms MBL-1 and MBL-2 from rainbow trout (Oncorhynchus mykiss) is presented. The deduced amino acid sequences of trout MBL-1 and MBL-2 (185 and 186 aa, respectively) present 83% identity to each other, exhibiting the highest identity score 46, 46 and 42% with the Atlantic salmon, shishamo smelt and zebrafish counterparts, respectively. The identity to birds and mammalian MBLs ranges from 25 to 33%. The trout MBL-1 and MBL-2 contain the EPN motif of mannose-binding C-type lectins, important for mannose specificity and they are expressed exclusively in liver and spleen, respectively.

Actins↗
PubMed2026

LitCTL1: A novel C-type lectin involved in the mucosal and cellular immunity of the common periwinkle Littorinalittorea.

C-type lectins (CTLs) are vital pattern-recognition receptors (PRRs) that mediate innate immune responses in mollusks, yet their characterization in Caenogastropoda, the largest gastropod group, remains limited. This study characterizes LitCTL1, a novel secreted single-domain C-type lectin from the common periwinkle, Littorina littorea. The 199-amino acid polypeptide contains a conserved carbohydrate recognition domain with canonical QPD and WND motifs and is predicted to form a homodimer. Uniquely, LitCTL1 was localized in both circulating hemocytes and mucus-secreting epithelial cells of the foot, mantle, and hypobranchial gland - the first report of such dual localization for a molluscan lectin, linking systemic and mucosal defense. Expression analysis revealed that LitCTL1 is constitutively expressed in hemocytes. Functional assays with recombinant LitCTL1 demonstrated its role as a potent opsonin with hemagglutinating activity, significantly enhancing hemocyte spreading and the phagocytosis of zymosan. Genomic analysis reveals that LitCTL1 belongs to a rapidly diversifying, genus-specific expansion distinct from conserved perlucin-like lineages. These results identify LitCTL1 as a key effector molecule in both systemic and mucosal innate immunity, likely reflecting an evolutionary adaptation to the microbial challenges of the intertidal environment.

Animals↗
PubMed2006

Characterization and cytotoxicity of mixed polyethyleneglycol modified liposomes containing doxorubicin.

Liposomes are recognized as one of the useful drug carriers, but have many problems to overcome before their clinical application. Liposomes, bonding peculiarly with serum protein (opsonization), are taken up by reticuloendothelial system (RES) cells in the liver and spleen. It is known that polyethyleneglycol (PEG) modification of the liposome surface induces the formation of a fixed aqueous layer around the liposomes due to the interaction between the PEG-polymer and water molecule, and thus prevents the attraction of opsonins. Namely, PEG-modified liposomes are able to escape trapping by the RES cells, and have a prolonged circulation time. In this study, the effects of different anchors with the same PEG molecular weight on the cell uptake and cytotoxicity of mixed PEG-modified liposomal doxorubicin (DOX) were examined. The fixed aqueous layer thickness (FALT) of liposomes covered with mixtures of PEG-molecules which differ in their chain length were increased, compared to that of the single PEG2000-modified liposome. Mixed PEG-modification of liposomes with different anchors (PEG2000-(1-monomethoxypolyethyleneglycol-2,3-distearoylglycerol (DSG): cholesterol (CHO)=1:1)-modified liposome) led to an increase in the FALT, compared to that of each single PEG-modification. The uptake of DOX into Ehrlich ascites carcinoma cells by the liposomes covered with PEG-CHO was higher than the other liposomes. Thus, liposomes covered with PEG-DSG and PEG-CHO have an enhanced cytotoxicity. In conclusion, it was confirmed that mix-modified liposomes using PEG-lipid with different anchors were superior.

Animals↗
PubMed2006

Accelerated blood clearance of PEGylated liposomes upon repeated injections: effect of doxorubicin-encapsulation and high-dose first injection.

The "accelerated blood clearance (ABC) phenomenon", causing PEGylated liposomes to be cleared very rapidly from the circulation upon repeated injection, has been reported to occur in rodents and rhesus monkeys. This rapid clearance was reported to be caused by the binding of PEG-specific IgM, which was generated by the first dose of injected liposomes, to the second dose of liposomes and the subsequent activation of complement, serving in turn as an opsonin. Although there are several PEGylated liposomal formulations, such as Doxil/Caelyx loaded with doxorubicin (DXR), in clinical use, the rapid clearance phenomenon has never been reported for such formulations. In the present article, we report that a first injection of PEGylated liposomes containing encapsulated DXR failed to induce the ABC phenomenon. Likewise, no rapid clearance of the test dose was observed when the first dose of "empty" PEGylated liposomes (without DXR) exceeded 5 micromol phospholipids/kg. By contrast, "empty" PEGylated liposomes at a low dose (1 micromol phospholipids/kg) induced the phenomenon as before. Western blot analysis revealed abundant binding of IgM to PEGylated liposomes when these were incubated in serum from rats that had received "empty" PEGylated liposomes. Substantially less binding of IgM was found when the liposomes were incubated in serum from rats treated with DXR-loaded PEGylated liposomes. For both the empty and the DXR-containing liposomes the amounts of IgM binding to the liposomes decreased with an increasing dose of injected liposomes. Serum obtained from rats following injection of empty PEGylated liposomes caused complement activation by addition of PEGylated liposomes in an inversely dose-dependent manner: the lower the dose, the higher the complement activation. By contrast, no complement activation was detected with serum from rats that had been treated with DXR-loaded PEGylated liposomes. These findings suggest that encapsulation of DXR as well as a relatively high lipid dose abrogate the immune response against PEGylated liposomes which is observed with the same liposomes but without DXR and at low doses. Our observations may thus have important implications for the development, evaluation and therapeutic use of liposomal cytotoxic drug formulations requiring multiple injection schemes.

Animals↗