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S Gordon

Publications and source records attributed to S Gordon.

At least 37 records · Page 2Linked to original sources
PubMed2000

Macrophage class A scavenger receptor-mediated phagocytosis of Escherichia coli: role of cell heterogeneity, microbial strain, and culture conditions in vitro.

Macrophage class A scavenger receptors (SR-AI and SR-AII) contribute to host defense by binding polyanionic ligands such as lipopolysaccharide and lipoteichoic acid. SR-A knockout (SR-A(-/-)) mice are more susceptible to endotoxic shock and Listeria monocytogenes infection in vivo, possibly due to decreased clearance of lipopolysaccharide and microorganisms, respectively. We have used flow cytometry to analyze the role of SR-A and other scavenger-like receptors in phagocytosis of bacteria in vitro. Chinese hamster ovary cells stably transfected with human SR-A bound Escherichia coli and Staphylococcus aureus but ingested few organisms. Primary human monocyte-derived macrophages (Mphi) bound and ingested E. coli more efficiently, and this was partially but selectively blocked by the general SR inhibitor, poly(I). A specific and selective role for SR-A was shown, since bone marrow culture-derived Mphi from SR-A(-/-) mice ingested fewer E. coli organisms than did wild-type cells, while uptake of antibody-opsonized E. coli was unaffected. SR-A-dependent uptake of E. coli varied with the bacterial strain; ingestion of DH5alpha and K1 by SR-A(-/-) Mphi was reduced by 30 to 60% and 70 to 75%, respectively. Phagocytosis and endocytosis via SR-A were markedly down-modulated when Mphi were plated on serum-coated tissue culture plastic compared to bacteriologic plastic, where cell adhesion is mediated by SR-A and CR3, respectively. This paper demonstrates that SR-A can bind and ingest bacteria directly, consistent with a role in host defense in vivo, and highlights the importance of the source of the Mphi, bacterial strain, and culture conditions on receptor function in vitro.

Animals↗
PubMed2000

Serodiagnosis of Bartonella bacilliformis infection by indirect fluorescence antibody assay: test development and application to a population in an area of bartonellosis endemicity.

Bartonella bacilliformis causes bartonellosis, a potentially life-threatening emerging infectious disease seen in the Andes Mountains of South America. There are no generally accepted serologic tests to confirm the disease. We developed an indirect fluorescence antibody (IFA) test for the detection of antibodies to B. bacilliformis and then tested its performance as an aid in the diagnosis of acute bartonellosis. The IFA is 82% sensitive in detecting B. bacilliformis antibodies in acute-phase blood samples of laboratory-confirmed bartonellosis patients. When used to examine convalescent-phase sera, the IFA is positive in 93% of bartonellosis cases. The positive predictive value of the test is 89% in an area of Peru where B. bacilliformis is endemic and where the point prevalence of infection is 45%.

Antibodies, Bacterial↗
PubMed2000

Species identification and subtyping of Ureaplasma parvum and Ureaplasma urealyticum using PCR-based assays.

There is good evidence that the organism currently known as Ureaplasma urealyticum should be divided into two species-U. parvum (previously U. urealyticum biovar 1) and U. urealyticum (previously U. urealyticum biovar 2). In this study, we designed a series of primers, targeting the 16S rRNA gene and 16S rRNA-23S rRNA intergenic spacer regions, the urease gene subunits, and the 5' ends of the multiple-banded antigen (MBA) genes, to identify and subtype these Ureaplasma species. All of the species-specific primer pairs could distinguish the two species, but only subtype-specific primer pairs targeting the MBA genes could distinguish subtypes within each species. U. parvum was separated into three subtypes, represented by serovars 1, 3/14, and 6. U. urealyticum was also separated into three subtypes by PCR and/or direct sequencing. Subtype 1 consisted of serovars 2, 5, 8, and 9; subtype 2 contained serovars 4, 10, 12, and 13; and subtype 3 contained serovars 7 and 11. A selection of primer pairs was used to identify and subtype 78 clinical ureaplasma isolates from vaginal swabs of pregnant women and to identify and subtype ureaplasmas directly in 185 vaginal swabs in which they had been previously detected. U. parvum was identified in 228 (87%) of 263 isolates or specimens, and U. urealyticum was identified in 50 (19%) (both were present in 6%). Serovars 3/14 (48%) and 1 (43%) were most common among U. parvum isolates, and subtypes 2 (62%) and 1 (34%) were most common among U. urealyticum isolates. This new PCR-based typing system will facilitate future studies of the relationship between individual Ureaplasma species or subtypes and human disease.

Antigens, Bacterial↗
PubMed2000

A cluster of necrotizing enterocolitis in term infants undergoing open heart surgery.

BACKGROUND: Necrotizing enterocolitis (NEC) is a serious gastrointestinal disease of unknown cause that predominantly affects premature infants, but it has been reported in term infants with congenital heart disease. METHODS: In August and September of 1997, 4 cases of NEC in term infants with congenital heart disease were identified among 24 infants undergoing cardiac surgical procedures at our institution. Because nosocomial NEC had not previously been identified among infants in our pediatric intensive care unit, a case-control study was conducted to identify risk factors for NEC. All infants less than 4 months old undergoing cardiac surgery without development of NEC during the epidemic period were selected as controls. RESULTS: The only significant risk factor associated with case-infants was a higher mean temperature gradient (rectal/toe) during the immediate 12-hour postoperative period (4.0 degrees C vs 2.0 degrees C, P <.01). Urine output was higher in control-infants in this postoperative period, although not statistically significant (11.9 mL/h vs 6.1 mL/h, P =.15). CONCLUSION: Although an infectious etiology cannot be ruled out, the cases of NEC in infants with congenital heart disease after cardiac procedures may have resulted from mesenteric ischemia associated with a low perfusion state in the perioperative period.

Anti-Bacterial Agents↗
PubMed2000

Disability awareness: a checklist for the medical practice.

Although Congress passed the Americans with Disabilities Act (ADA) of 1990, our nation's 54 million people with disabilities continue to face many challenges when seeking health care. Physicians and their staffs can heighten their awareness and sensitivity to disability and provide better communication plus an organized system of care for patients with disabilities.

Adult↗
PubMed1999

The human eukaryotic initiation factor 4AI gene (EIF4A1) contains multiple regulatory elements that direct high-level reporter gene expression in mammalian cell lines.

The gene encoding human eukaryotic initiation factor 4A (EIF4A1) is located on chromosome 17p13, 667 bp upstream from the gene encoding the macrophage endosomal protein CD68. The EIF4AI gene contains 10 intervening sequences with the 1397-bp first intron containing a CpG-rich methylation-free island. Sequences capable of enhancing gene expression reside between positions -69 and -371 and positions -504 and -1100 of the EIF4AI 5' flanking sequence and within introns 1, 2, 3, 7, and 9. In macrophage cell lines, EIF4A1 expression vectors give sustained high-level reporter gene expression to levels 10 times higher than that obtained using the human cytomegalovirus immediate-early gene promoter/enhancer. Sequences of the human EIF4AI gene may find application in the development of new vectors for gene therapy and genetic vaccination.

5' Untranslated Regions↗
PubMed1999

Cell-specific glycoforms of sialoadhesin and CD45 are counter-receptors for the cysteine-rich domain of the mannose receptor.

We previously reported that CR-Fc, an Fc chimeric protein containing the cysteine-rich (CR) domain of the mannose receptor, binds to marginal zone metallophilic macrophages (Mo) and B cell areas in the spleen and to subcapsular sinus Mo in lymph nodes of naive mice (CR-Fc(+) cells). Several CR-Fc ligands were found in spleen and lymph node tissue lysates using ligand blots. In this paper we report the identification of two of these ligands as sialoadhesin (Sn), an Mo-specific membrane molecule, and the leukocyte common antigen, CD45. CR-Fc bound selectively to Sn purified from spleen and lymph nodes and to two low molecular weight isoforms of CD45 in a sugar-dependent manner. CR-Fc binding and non-binding forms of Sn, probably derived from CR-Fc(+) and CR-Fc(-) cells respectively, were selected from spleen lysates. Analysis of the glycan pool associated with the CR-Fc-binding form revealed the presence of charged structures resistant to sialidase, absent in the non-binding form, that could correspond to sulfated structures. These results confirm the identification of the CR region of the mannose receptor as a lectin. We also demonstrate that the same glycoprotein expressed in different cells of the same organ can display distinct sugar epitopes that determine its binding properties.

Animals↗
PubMed1999

A member of the dendritic cell family that enters B cell follicles and stimulates primary antibody responses identified by a mannose receptor fusion protein.

Dendritic cells (DCs) are known to activate naive T cells to become effective helper cells. In addition, recent evidence suggests that DCs may influence naive B cells during the initial priming of antibody responses. In this study, using three-color confocal microscopy and three-dimensional immunohistograms, we have observed that in the first few days after a primary immunization, cells with dendritic morphology progressively localize within primary B cell follicles. These cells were identified by their ability to bind a fusion protein consisting of the terminal cysteine-rich portion of the mouse mannose receptor and the Fc portion of human immunoglobulin (Ig)G1 (CR-Fc). In situ, these CR-Fc binding cells express major histocompatibility complex class II, sialoadhesin, and CD11c and are negative for other markers identifying the myeloid DC lineage, such as (CD11b), macrophages (F4/80), follicular DCs (FDC-M2), B cells (B220), and T cells (CD4). Using CR-Fc binding capacity and flow cytometry, the cells were purified from the draining lymph nodes of mice 24 h after immunization. When injected into naive mice, these cells were able to prime T cells as well as induce production of antigen-specific IgM and IgG1. Furthermore, they produced significantly more of the lymphocyte chemoattractant, macrophage inflammatory protein (MIP)-1alpha, than isolated interdigitating cells. Taken together, these results provide evidence that a subset of DCs enters primary follicles, armed with the capacity to attract and provide antigenic stimulation for T and B lymphocytes.

Animals↗
PubMed1999

Mannose receptor and its putative ligands in normal murine lymphoid and nonlymphoid organs: In situ expression of mannose receptor by selected macrophages, endothelial cells, perivascular microglia, and mesangial cells, but not dendritic cells.

The mannose receptor (MR) has established roles in macrophage (Mphi) phagocytosis of microorganisms and endocytic clearance of host-derived glycoproteins, and has recently been implicated in antigen capture by dendritic cells (DCs) in vitro. MR is the founder member of a family of homologous proteins, and its recognition properties differ according to its tissue of origin. Given this heterogeneity and our recent discovery of a soluble form of MR in mouse serum, we studied the sites of synthesis of MR mRNA and expression of MR protein in normal mouse tissues. We demonstrate that synthesis and expression occur at identical sites, and that mature Mphi and endothelium are heterogeneous with respect to MR expression, additionally describing MR on perivascular microglia and glomerular mesangial cells. However, MR was not detected on DCs in situ, or on marginal zone or subcapsular sinus Mphi, both of which have MR-like binding activities. We also compared expression of MR to the binding of a recombinant probe containing the cysteine-rich domain of MR. We show that MR and its putative ligand(s) are expressed at nonoverlapping sites within lymphoid organs, consistent with a transfer function for soluble MR. Therefore, in addition to endocytic and phagocytic roles, MR may play an important role in antigen recognition and transport within lymphoid organs.

Animals↗
PubMed1999

Type 1 and type 2 cytokine regulation of macrophage endocytosis: differential activation by IL-4/IL-13 as opposed to IFN-gamma or IL-10.

Cytokine regulation of endocytic activity in primary human macrophages was studied to define ultrastructural changes and mechanisms of pinocytic regulation associated with cytokines secreted by activated T cells. The effects of IFN-gamma (type 1) and IL-4/IL-13 and IL-10 (type 2) cytokines on fluid phase and mannose receptor-mediated endocytosis were assessed by horseradish peroxidase and colloidal gold-BSA uptake and computer-assisted morphometric analysis. IL-4 and IL-13 enhanced fluid phase pinocytosis and mannose receptor-mediated uptake by activation of phosphatidylinositol 3-kinase. Inhibition of actin assembly showed that both cytokines exerted actin-dependent and -independent effects. Ultrastructurally, IL-4 and IL-13 increased tubular vesicle formation underneath the plasma membrane and at pericentriolar sites, concurrent with decreased particle sorting to lysosomes. By contrast, IL-10 or IFN-gamma decreased both fluid phase pinocytosis and mannose receptor-mediated uptake. IFN-gamma stimulated increased particle sorting to perinuclear lysosomes, while IL-10 decreased this activity. In summary, our data document differential effects on macrophage endocytic functions by type 1 or type 2 cytokines associated with induction and effector pathways in immunity.

Actins↗
PubMed1999

Phagocytosis stimulates alternative glycosylation of macrosialin (mouse CD68), a macrophage-specific endosomal protein.

Macrosialin (mouse CD68), a macrophage-specific member of the lysosomal-associated membrane protein family, displays N-linked glycosylation and a heavily sialylated, mucin-like domain. We show that phagocytosis of zymosan by inflammatory peritoneal macrophages potently alters glycan processing of macrosialin in vitro. The phagocytic glycoform is not induced by other forms of endocytosis and depends on particle internalization. Zymosan uptake does not influence macrosialin protein synthesis, but increases the specific incorporation of D-[2-3H]mannose, D-[6-3H]galactose, N-acetyl-D-[1-3H]glucosamine and L-[5,6-3H]fucose by 2-15-fold. The phagocytic glycoform displays increased binding of agglutinins from peanut, Amaranthus caudatus and Galanthus nivalis, whereas binding of the sialic-acid-specific Maakia amurensis agglutinin is slightly reduced. Digestion by N-Glycanase abolishes the incorporation of [3H]mannose label and Galanthus nivalis agglutinin binding activity, but preserves the incorporation of galactose and N-acetylglucosamine and specific lectin binding. We also show that phagocytosis increases the complexity and length of O-linked chains. The data presented highlight the importance of differential glycosylation in the biology of macrosialin, phagosomes and macrophages in general.

Animals↗
PubMed1999

Previous uptake of apoptotic neutrophils or ligation of integrin receptors downmodulates the ability of macrophages to ingest apoptotic neutrophils.

Clearance of apoptotic neutrophils (polymorphonuclear leukocyte [PMN]) by macrophages is thought to play a crucial role in resolution of acute inflammation. There is increasing evidence that ingestion of apoptotic cells modulates macrophage behavior. We therefore performed experiments to determine whether ingestion of apoptotic PMN modulated the uptake process itself. Rat bone marrow-derived macrophages (BMDM) ingested apoptotic PMN by a process that was enhanced by tumor necrosis factor (TNF) and attenuated by interferon (IFN)-gamma, interleukin (IL)-4, and IL-10. It was inhibitable by the tetrapeptide arg-gly-gln-ser (RGDS), therefore implicating the alphavbeta3/CD36/thrombospondin pathway. Interaction of apoptotic PMN with BMDM for 30 minutes, 48 hours before rechallenge reduced uptake of apoptotic PMN by 50% compared with previously unchallenged BMDM. Blocking initial uptake with RGDS abrogated the effect of preexposure. Comparable and sustained attenuation of uptake was obtained by ligating alphavbeta3 with the monoclonal antibody (MoAb), F11, after a delay of more than 90 minutes, whereas MoAbs to CD25 and CD45 had no effect. Ligation of alpha6beta1 and alpha1beta2, integrins not previously implicated in the engulfment of apoptotic cells also decreased uptake with similar kinetics to F11. Therefore, apoptotic PMN regulate their own uptake through an integrin-dependent process, which can be reproduced by ligation of other integrins expressed by macrophages.

Animals↗
PubMed1999

Regulation and functional involvement of macrophage scavenger receptor MARCO in clearance of bacteria in vivo.

The scavenger receptors expressed by macrophages are thought to play an important role in the immune response against bacteria by mediating binding and phagocytosis. A novel member of the class A scavenger receptor family, macrophage receptor with collagenous structure (MARCO), has recently been identified. In this study we have generated a panel of mAbs with specificities for different domains of this receptor. Two of those reacting with the C-terminal cysteine-rich domain block ligand binding of MARCO. The in vivo expression of this murine receptor is normally restricted to distinct populations of macrophages in the spleen and lymph nodes. During bacillus Calmette-Guérin (BCG) infection, during bacterial sepsis, or after the injection of purified LPS, however, the expression of MARCO is rapidly induced on macrophages in other tissues, including Kupffer cells in the liver. Using the mouse macrophage cell line J774.2, it was shown that LPS stimulation up-regulates surface expression of MARCO in a dose- and time-dependent fashion. The proinflammatory cytokines IL-1, IL-6, TNF-alpha, and IFN-gamma had little or no effect. Using inhibitory mAbs, the relevance of MARCO for the clearance of circulating bacteria in vivo was determined. Although the overall elimination of live Escherichia coli and Staphylococcus aureus from the blood did not appear to be affected by treatment with these Abs, the capturing of heat-killed bacteria by macrophages in the marginal zone areas of the spleen was clearly inhibited. This study suggests a role for MARCO in the host antibacterial defense.

Animals↗
PubMed1999

Lack of effect of intravenous administration on time to respond to azathioprine for steroid-treated Crohn's disease. North American Azathioprine Study Group.

BACKGROUND & AIMS: Azathioprine is effective for Crohn's disease but acts slowly. A loading dose may decrease the time to response. METHODS: A placebo-controlled study was conducted in patients with active Crohn's disease despite prednisone treatment. Patients were randomized to a 36-hour infusion of azathioprine, 40 mg/kg (51 patients), or placebo (45 patients) followed by oral azathioprine, 2 mg/kg, for 16 weeks. Prednisone was tapered over 5 weeks. The primary outcome measure was complete remission at week 8, defined by discontinuation of prednisone and a Crohn's Disease Activity Index of </=150 points. Erythrocyte concentrations of the azathioprine active metabolite, 6-thioguanine nucleotide, were measured. RESULTS: At week 8, 13 patients (25%) were in complete remission in the azathioprine-loaded group compared with 11 patients (24%) in the placebo group. The frequency of complete remission did not increase after 8 weeks in either group. Both groups achieved steady state of 6-thioguanine nucleotide by week 2, and no differences were found in mean concentrations between the groups. There were no significant differences in the frequency of adverse events between the groups. CONCLUSIONS: A loading dose does not decrease the time to response in patients with steroid-treated Crohn's disease beginning azathioprine therapy. Steady state of erythrocyte 6-thioguanine nucleotide and complete response occurred earlier than previously reported.

Administration, Oral↗
PubMed1999

Exposure-response relationships for work-related sensitization in workers exposed to rat urinary allergens: results from a pooled study.

BACKGROUND: Recent studies in a few industries have shown that the likelihood of IgE-mediated sensitization increases with increasing exposure. The shape of the exposure-response relationships and modification by age, sex, and smoking habit has hardly been studied. OBJECTIVE: The purpose of this study was to determine exposure sensitization relationships for rat sensitization and to evaluate the influence of atopy, smoking habits, and sex. METHODS: Data from 3 cross-sectional studies in The Netherlands, the United Kingdom, and Sweden were used and involved 1062 animal laboratory workers. Selection criteria were harmonized, and this resulted in a study population of 650 animal laboratory workers (60.6% female) with less than 4 years of exposure. Air allergen levels were assessed previously and converted on the basis of an interlaboratory allergen analysis comparison. Available sera were analyzed for the presence of specific antibodies against common allergens (house dust mite, cat, dog, and grass and birch pollen) and work-related allergens (rat and mouse urinary proteins). Questionnaire items on work-related respiratory symptoms, hours worked with rats per week, job performed, smoking habits, and sex were used in this analysis RESULTS: The prevalence of work-related sensitization to rat urinary allergens (IgE >0.7 KU/L) was 9.7 % (n = 63). Thirty-six of the sensitized workers had work-related symptoms (asthma or rhinitis). Two hundred forty-eight workers (38.2%) were atopic (defined as specific IgE to 1 of the common allergens). The sensitization rate increased with increasing air allergen exposure. Atopic workers exposed to low levels of allergen had a more than 3-fold increased sensitization risk compared with nonexposed atopic workers. For atopic subjects, the risk increased little with increasing exposure, whereas for nonatopic subjects, a steadily increasing risk was observed. Smoking and sex did not modify the sensitization risk. CONCLUSION: Rat urinary allergen-sensitization risk increased with increasing exposure intensity. Workers who were atopic had a clearly elevated sensitization risk at low allergen exposure levels.

Allergens↗
PubMed1999

Macrophage-restricted molecules: role in differentiation and activation.

Membrane antigens serve as excellent markers of murine macrophage (MO) differentiation in vivo and in vitro, and have yielded insights into novel MO functions in innate and acquired immunity. We review briefly the use of a range of monoclonal antibodies against MO which show restricted expression: F4/80, macrosialin and sialoadhesin. Differential display PCR strategies have made it possible to identify a novel MO-restricted membrane molecule, a murine MO C-type lectin (mMCL). The isolation of functionally active ab against known receptors such as the scavenger receptor, Class A (SR-A) has provided a key reagent to characterise the role of this molecule in adhesion, endocytosis, phagocytosis and in the regulation of cellular immunity. Studies in SR-A ko mice challenged with BCG and LPS show that the SR-A molecule helps to limit excessive production of cytokines such as TNFalpha by MO that have been activated by infection, and thus protects the host against septic shock.

Animals↗