Biomedical subjects

M Oppermann

Publications and source records attributed to M Oppermann.

At least 55 records · Page 3Linked to original sources

PubMed1995

Differential expression of complement receptors on human basophils and mast cells. Evidence for mast cell heterogeneity and CD88/C5aR expression on skin mast cells.

Complement-dependent activation of immune cells is regulated by cell surface membrane receptors. In this study, expression of complement receptors (CR) on human blood basophils (n = 11), tissue mast cells (lung, n = 7; skin, n = 10; uterus, n = 4; tonsil, n = 3; heart, n = 10), and on respective human cell lines (basophil line KU-812, mast cell line HMC-1) was analyzed by the use of mAbs and indirect immunofluorescence. Normal blood basophils and KU-812 cells were found to express C5aR (CD88), membrane cofactor protein (CD46), decay-accelerating factor (CD55), and membrane attack complex inhibitory factor (CD59), as well as the previously recognized CR1 (CD35), CR3 alpha (CD11b), CR4 alpha (CD11c), and CR3/4 beta (CD18). Mast cells from all organs as well as HMC-1 cells expressed CD46, CD55, and CD59, but not CD11b, CD21, or CD35. The C5aR (CD88) was detectable on skin mast cells, a subset (5 to 15%) of cardiac mast cells, and on HMC-1 cells, but not on lung, uterus, or tonsillar mast cells (< 5%). Moreover, double immunoperoxidase staining (tryptase vs C5aR/CD88) revealed in situ expression of C5aR on skin, but not lung mast cells. Recombinant human (rh) C5a, at 10(-10) to 10(-7) M, induced secretion of histamine from basophils (rhC5a, 10(-8) M: 53.4 +/- 3.1% vs control < 5%) and from skin mast cells (rhC5a, 10(-8) M: 25.8 +/- 16.1% vs control < 10% histamine release), but not from other mast cells (rhC5a or control: < 10%, p > 0.05). The rhC5a-induced secretion of histamine from basophils and skin mast cells was inhibited by S5/1, a blocking Ab against CD88 (basophils: 37.2% to 75.1%; skin mast cells: 39.2% to 83.9% inhibition, p < 0.05). Together, this study shows that a) basophils and mast cells express a different profile of complement receptors, b) C5a-dependent mediator release in skin mast cells and basophils is mediated via CD88, and c) mast cells constitute a heterogeneous lineage in terms of expression of the C5a binding site CD88.

Antigens, CD↗

PubMed1995

Improvement in the long-term stability of an amperometric glucose sensor system by introducing a cellulose membrane of bacterial origin.

Classical amperometric glucose sensors that use cellulose membranes of wood origin (Cuprophan) suffer from the fact that their long-term stability in blood is short; therefore, their clinical use is limited. In the present study, a classical amperometric glucose sensor was covered with a bacterial cellulose (BC) membrane. Its surface in comparison to that of the classical glucose sensor (Cuprophan) and its long-term stability were tested in vitro and in vivo. The surface element composition was approximately 44% oxygen and approximately 56% carbon in both membranes and thus typical for cellulose. BC membranes exhibited fiber structure, whereas cup membranes did not. There was also a qualitative difference in protein adsorption between both membranes on exposure to bovine serum albumin. Treatment with Trogamid of one site of the BC membranes allowed linear glucose detection between 0 and 40 mM. Hemocompatibility of BC membranes was improved in comparison to cup membranes on the basis of complement activation (C3a and C5a). In diluted blood (1:10), the BC-covered sensor exhibited a long-term stability of more than 200 h; in undiluted blood it was stable for about 24 h, which is about 6-7 times longer than the stability of the classical Cup membrane-covered sensor. In in vivo studies, where the BC membrane-covered sensors were connected to the jugular vein of rats, blood glucose levels could be monitored for at least 24 h. In summary, the use of a modified bacterial cellulose membrane to cover the classical amperometric glucose sensor significantly improves the sensor's long-term stability both in vitro and in vivo.

Acetobacter↗

PubMed1995

Terminal complement pathway activation and low lysis inhibitors in rheumatoid arthritis synovial fluid.

OBJECTIVE: To investigate terminal complement activation and lysis inhibitors in rheumatoid arthritis (RA). METHODS: C5a, vitronectin and clusterin were quantitated by enzyme immunoassays in plasma and synovial fluid (SF) in RA (n = 30) and osteoarthritis (OA) (n = 11). RESULTS: In RA the concentration of C5a was 3-fold increased in plasma (21.9 vs 7.2 micrograms/l) and 5-fold increased in SF (7.8 vs 1.7 micrograms/l) compared to OA. The SF/plasma ratios for C5a, vitronectin and clusterin were 0.35, 0.36 and 0.23, respectively, not significantly different in the 2 diseases. CONCLUSION: SF terminal pathway activation in RA combined with low local levels of lysis inhibitors might allow lytic or sublytic attacks on local cells, resulting in inflammation and cell damage.

Arthritis, Rheumatoid↗

PubMed1994

C3a activates the respiratory burst in human polymorphonuclear neutrophilic leukocytes via pertussis toxin-sensitive G-proteins.

In contrast to C5a, which represents a well-established potent activator of the respiratory burst in polymorphonuclear neutrophilic granulocytes (PMN), the functional role of C3a in the activation of PMN is, so far, poorly understood. Herein, the potential role of human C3a in the activation of the respiratory burst in human PMN was investigated. The release of reactive oxygen species (ROS) of PMN from healthy donors was measured by lucigenin-dependent chemiluminescence. C3a dose-dependently induced the production of ROS in human PMN in the range between 10 ng/mL and 1,000 ng/mL, whereas C3a-desArg was inactive. Flow cytometric measurement of H2O2 by dihydrorhodamine-123 labeling of anti-CD16-stained PMN showed that predominantly neutrophilic PMN are responsible for the C3a-induced activation of the respiratory burst. To exclude that C3a stimulation was caused by contamination with C5a, the specificity of C3a-induced activation of PMN was shown using monoclonal antibodies (MoAbs). Accordingly, the effect of C3a was completely abolished in the presence of Fab fragments of a blocking anti-C3a MoAb. In addition, blockade of the C5a receptor by the anti-C5a receptor (anti-C5aR) MoAb, S5/1, totally inhibited the C5a-induced production of ROS, whereas the C3a response in the presence of the anti-C5aR MoAb was unaffected. The specificity of the response was further confirmed by homologous desensitization after restimulation with C3a. In contrast, no cross-desensitization was observed upon stimulation with C5a. The C3a-induced ROS production by PMN was inhibited by pertussis toxin, indicating the involvement of guanine nucleotide-binding proteins (Gi proteins) in the signal transduction process initiated by C3a. In addition, stimulation of PMN by C3a resulted in a transient increase in the cytosolic free calcium concentration ([Ca2+]i) in a dose-dependent manner. In contrast to C3a-induced ROS production, C3a did not induce a chemotactic response in PMN, indicating functional qualitative differences as compared with C5a. In summary, these results show that C3a is a potent activator of the respiratory burst in human PMN. Therefore, these findings point to a novel role of C3a in the pathogenesis of inflammatory diseases associated with increased C3a levels and PMN activation.

Calcium↗

PubMed1994

C3a activates reactive oxygen radical species production and intracellular calcium transients in human eosinophils.

Whereas C5a is a well-established potent activator of eosinophils, the functional role of C3a in the activation of eosinophils is, so far, poorly understood. Here, the activation of human eosinophils stimulated with C3a was analyzed and compared to C5a activation. Flow-cytometrical measurements revealed that stimulation of eosinophils by C3a resulted in a transient elevation of the intracellular calcium concentration ([Ca2+]i) in a dose-dependent manner. In addition, the production of reactive oxygen radical species (ROS) of eosinophils after C3a and C5a stimulation was measured by lucigenin-dependent chemiluminescence and quantified by superoxide dismutase-inhibitable reduction of ferricytochrome C. Half maximal and maximal ROS production in response to C3a was observed at 50 ng/ml and 1000 ng/ml, respectively, whereas C3a-desArg was inactive. To ensure that C3a stimulation was not caused by contamination with C5a, monoclonal antibodies were used to demonstrate the specificity of C3a. The effect of C3a was completely abolished in the presence of monovalent antigen-binding fragments of a functionally blocking anti-C3a monoclonal antibody. In addition, blockade of the C5a receptor by the monoclonal anti-C5a receptor antibody S5/1 totally inhibited the C5a-evoked ROS production, whereas the C3a response in the presence of S5/1 was unaffected. Finally, desensitization experiments revealed a homologous desensitization of C3a after restimulation with C3a. In contrast, no cross-desensitization was observed upon stimulation with C5a. Furthermore, the C3a- and C5a-induced production of ROS of eosinophils was totally inhibited by pertussis toxin, indicating the involvement of guanine nucleotide-binding proteins (Gi-proteins). In summary, these results demonstrate that C3a is a potent activator for eosinophils initiating transient [Ca2+]i changes and production of reactive oxygen species. C3a therefore may play a part in the pathophysiology of diseases with eosinophil and complement activation.

Calcium↗

PubMed1994

Characterization of physiologic breakdown products of the complement fragment Ba.

To better characterize the activation products of factor B which are generated under physiologic conditions Ba was purified directly from human EDTA-plasma by immunoaffinity chromatography using anti-Ba Sepharose. SDS-PAGE analysis revealed the existence of degradation products of the Ba fragment which were truncated at the carboxyterminus. A monoclonal antibody (mAb D22/3) was produced by immunizing mice with a synthetic peptide which corresponds to the Ba carboxyterminus (Glu215-Arg234). This mAb was found to react with an epitope (Ba neo-epitope), which is newly formed after the generation of Ba from its precursor protein factor B. This neoantigenic determinant is absent both in factor B and the desArg/Lys Ba derivatives. The conversion of Ba by carboxypeptidases in human serum was monitored using an assay which is based on mAb D22/3, revealing a half-life of Ba in serum of 150 min. Furthermore, this assay allowed to quantitate plasma levels of intact and degraded Ba in healthy probands and in patients with chronic renal failure. The processing of the Ba carboxyterminus may be of functional relevance as the biological activity of the Ba fragment which had been shown to suppress human B lymphocyte functions in vitro resides in its carboxyterminal amino acid sequence.

Amino Acid Sequence↗

PubMed1994

Plasma clearance of the human C5a anaphylatoxin by binding to leucocyte C5a receptors.

The C5a anaphylatoxin is a potent complement-derived mediator of inflammation with chemotactic activity. In this study the possible role of specific high-affinity binding sites for C5a on peripheral blood leucocytes for the removal of C5a from human blood plasma was investigated. The addition of purified granulocytes or mononuclear cells to complement-activated plasma resulted in the rapid and dose-dependent removal of up to 80% of plasma C5a, as determined by ELISA. The specific role of leucocyte C5a receptors (C5aR) in the plasma clearance of C5a was demonstrated by the inhibition of C5a uptake by the preincubation of cells with the C5aR-specific monoclonal antibody S5/1. Furthermore, U937 cells which had been induced by db-cAMP to express C5aR, but not undifferentiated U937 cells, were capable of removing C5a from plasma. The inhibition of C5aR internalization by monensin did not affect C5a uptake by leucocytes. The co-incubation with leucocytes had no effect on the plasma clearance of complement activation products C3a or terminal complement complex (TCC), as determined by this in vitro assay. The binding of the C5a anaphylatoxin to cellular receptors represents an effective control mechanism that protects the organism from systemic effects of this potent phlogistic mediator.

Antibodies, Monoclonal↗

PubMed1994

Association of pulmonary inflammation and increased microvascular permeability during the development of bronchopulmonary dysplasia: a sequential analysis of inflammatory mediators in respiratory fluids of high-risk preterm neonates.

OBJECTIVE: Bronchopulmonary dysplasia (BPD) of preterm neonates is associated with an increased recruitment of inflammatory cells into the airways. To evaluate further the role of inflammation in the pathogenesis of BPD, tracheobronchial aspirate fluid of neonates with birth weight < 1200 g (n = 59) was sequentially analyzed in a prospective study. METHODS: Tracheobronchial aspirate fluid was assessed for chemotactic activity, neutrophil cell count, concentrations of elastase-alpha 1-proteinase inhibitor and activity of free elastase, concentrations of chemoattractants (complement component C5-derived anaphylatoxin, leukotriene B4, interleukin-8), and albumin concentrations as well as alpha 1-proteinase inhibitor activity. The secretory component for immunoglobulin A was used as reference protein. Only specimens without evidence of microbiological colonization were studied. RESULTS: In neonates with prolonged respiratory disease (BPD-risk neonates, n = 24, fraction of inspired oxygen > or = 0.3 and/or peak inspiratory pressure > or = 16 cm H2O at day 10 postnatal age, birth weight 892 +/- 36 g, gestational age 27.2 +/- 0.3 weeks) chemotactic activity, cell count, concentrations of the chemoattractants complement component C5-derived anaphylatoxin, leukotriene B4, interleukin-8, as well as levels of elastase-alpha 1-proteinase inhibitor were significantly higher at day 10 and/or day 15 of postnatal age compared with neonates without chronic pulmonary disease (total n = 35; day 10, n = 11; day 15, n = 8). There was no difference in free elastolytic activity. Concentrations of albumin as well as alpha 1-proteinase inhibitor activity were higher in BPD-risk patients on day 15, indicating an increased pulmonary leak. CONCLUSION: We conclude that preterm neonates at risk for the development of BPD show an enhanced inflammatory reaction in the lungs and an associated increase in pulmonary microvascular permeability. We speculate that inflammation may play an important role in the pathogenesis of BPD.

Albumins↗

PubMed1993

Probing the human receptor for C5a anaphylatoxin with site-directed antibodies. Identification of a potential ligand binding site on the NH2-terminal domain.

Molecular cloning has revealed the DNA sequence of the human receptor for the C5a anaphylatoxin (C5aR). In this study, mAb and polyclonal antibodies with specificities for deduced hydrophilic sequences of the receptor protein were employed to determine the expression and the topography of C5aR on PBL. Evidence was obtained that an antigenically homogenous receptor exists on human neutrophils, eosinophils, and monocytes that binds C5a and C5a(desArg). The assignment of epitopes to extra- or intracellular receptor domains as determined by FACS analysis of intact or permeabilized cells confirmed the general topography of the C5aR that had been predicted by hydropathy analysis. Competitive binding studies were performed to examine whether extracellular receptor domains participate in ligand binding. The occupation of the receptor by C5a inhibited only the binding of antibodies that were specific for the receptor's aminoterminal domain (C5aR-EX1). The anti-EX1 mAb S5/1 effectively antagonized C5a/C5a(desArg) biological activity. A heptameric peptide (D15DKDTLD21) was identified as the smallest receptor fragment that was recognized by the mAb S5/1 or by polyclonal rabbit anti-EX1 lg. These results imply that an amino acid sequence rich in aspartate within the receptor aminoterminus represents both an immunodominant epitope and a ligand binding site on the C5aR.

Amino Acid Sequence↗

PubMed1993

Proteins separated from human IgG molecules.

Immunoglobulin G binding proteins were separated from human IgG molecules using 1 N acetic acid followed by 5 M guanidinium chloride in 0.1 M acetic acid. The proteins thus obtained were heterogeneous as demonstrated by SDS-PAGE and reverse-phase HPLC. The isolated proteins consisted of two types: the C3a and C4a complement fragments (anaphylatoxins) and immunoglobulin peptide chain fragments V kappa I and C gamma 3. Both anaphylatoxins immobilized on cellulose nitrate membranes could reassociate with intact IgG molecules. The ubiquitous presence of C3a in IgG preparations was demonstrated using monoclonal antibodies specific for C3a. Nearly all of the bound anaphylatoxin molecules were found in the Fab fragment. These findings suggest that IgG molecules can eliminate anaphylatoxins from the circulation, and thus prevent harmful effects due to these active complement components.

Amino Acid Sequence↗

PubMed1993

Gene expression of interleukin-1 beta during hemodialysis.

It is still controversial whether the hemodialysis (HD) procedure is an inflammatory process in vivo. Therefore, we studied the gene expression of interleukin-1 beta (IL-1 beta) as a marker of inflammation in peripheral blood mononuclear cells (PBMC) of patients during HD by Northern blotting and polymerase chain reaction. Compared to PBMC separated pre-HD (1.0 densitometric units), the amount of IL-1 beta mRNA was increased in PBMC leaving the dialyzer (12.2 +/- 2 densitometric units, P < 0.01), but was not increased in PBMC re-entering the dialyzer from the systemic circulation (0.6 +/- 0.1 densitometric units) in all 12 patients studied. The maximal amount of IL-1 beta mRNA in PBMC was seen at five minutes after start of HD. There was a significant correlation between the increase in IL-1 beta mRNA and the increase in activated complement C5a (r = 0.71, P < 0.01). HD using less complement-activating membranes (hemophan, polysulfone, polyamide or polyacrylonitrile) resulted in no detectable IL-1 beta mRNA. Furthermore, a monoclonal antibody against human C5a reduced the increase in IL-1 beta mRNA by 83% (P < 0.05), indicating that C5a plays a major role for induction of IL-1 beta mRNA during HD. This study demonstrates that during HD with regenerated cellulose, gene expression for IL-1 beta takes place in PBMC.

Base Sequence↗

PubMed1993

Complement activation in septic baboons detected by neoepitope-specific assays for C3b/iC3b/C3c, C5a and the terminal C5b-9 complement complex (TCC).

We have investigated the cross-reactivity of various species in neoepitope-specific methods for quantification of human complement activation products. In contrast to most other species examined, baboon showed a substantial cross-reactivity supporting a high degree of homology between human and baboon complement. An assay for C3b, iC3b and C3c (MoAb bH6) showed moderately good reactivity, in contrast to a C3a assay which did not cross-react. Excellent reactivity was found for C5a using MoAbs C17/5 and G25/2. The reactivity of an established TCC assay (MoAb aE11 to a C9 neoepitope and polyclonal antibody to C5) was improved substantially by replacing the anti-C5 antibody with a new MoAb to C6 particularly selected on the basis of baboon cross-reactivity. Plasma samples from baboons receiving 2.5 x 10(9) and 1.0 x 10(10) live Escherichia coli bacteria/kg were examined with the assays described. In vivo complement activation with the lowest dose was moderate and kept under control, in contrast to the highest dose, where an uncontrolled increase in all activation products continued throughout the infusion period. These results support the hypothesis that sufficiently high amounts of endotoxin lead to uncontrolled activation of complement as seen in irreversible septic shock. The results are discussed with particular emphasis on activation of the terminal complement pathway.

Animals↗

PubMed1993

Interleukin-4 augments production of the third complement component by the alveolar epithelial cell line A549.

The elements of allergic inflammation and the involvement of helper T lymphocytes are increasingly being recognized in the immunopathogenesis of asthma. Allergen exposure leading to the activation of allergen-specific T cells present in the lung can result in the release of cytokines which in turn can locally stimulate the cellular constituents of the lung. The airway epithelial cells may be the key participants in such an interaction. Therefore, we examined the ability of T-cell-derived IL-4 to modulate the production of C3 and C5 by the human type-II pneumocyte cell line A549, which is known to produce all the components and the regulatory proteins of the complement system. For estimation of C3 an ELISA detecting native C3 was used. Following stimulation of A549 with hrIL-4 a dose-dependent (1-50 U/ml) enhancement of C3 production was observed, which reached its maximum (5-fold of unstimulated cells) at 48 h and gradually declined thereafter. Concentrations of hrIL-4 higher than 50 U/ml did not further increase C3 production. In parallel experiments hrIFN-gamma at concentrations between 10 and 50 U/ml stimulated the C3 production to more than twice the quiescent state level within 24 h. In the pneumocyte cell line A549 we demonstrated the expression of a gene for the IL-4 receptor which appears to mediate the biological effect of this lymphokine. A diminution in the functionally active C5, estimated by ELISA at the same time, was observed in supernatants of A549 cultures following stimulation with hrIL-4 as well as with hrIFN-gamma.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Line↗

PubMed1993

Levels of complement anaphylatoxin C5a in pulmonary effluent fluid of infants at risk for chronic lung disease and effects of dexamethasone treatment.

A number of studies have shown that increased numbers of neutrophils and macrophages are recruited into the airways during the development of chronic lung disease (CLD) in preterm infants. The objective of this study was to determine whether the anaphylatoxin C5a is detectable in tracheobronchial aspirate fluid of infants at risk for CLD and to evaluate the possible effects of dexamethasone (Dxm) treatment. C5a/C5a(des Arg) levels were determined by a sensitive ELISA based on a neoepitope-specific MAb. In a prospective study, 27 infants (birth weight 881 +/- 169 g, mean +/- SD) still on mechanical ventilation at d 10 postnatal age with fraction of inspired oxygen > or = 0.3 and/or peak inspiratory pressure > or = 16 cm H2O were randomly assigned to Dxm treatment at d 10 (n = 14) or d 16 (n = 13). Ten mechanically ventilated infants with no respiratory disease or who had recovered from respiratory distress syndrome did not meet these criteria on d 10 and served as a control group (birth weight 928 +/- 126 g). For the evaluation of Dxm therapy, the late treatment group was used as a control group for the early regimen. Compared with controls, C5a concentrations were higher in infants at risk for CLD on d 10 [median (25th-75th percentile): 2.40 (1.13-3.38) versus 0.82 (0.55-1.78) micrograms/L, p < 0.05].(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗

PubMed1993

Plasma levels of bactericidal/permeability-increasing protein (BPI) and lipopolysaccharide-binding protein (LBP) during hemodialysis.

Several proteins modify the biological response to lipopolysaccharide (LPS). Both bactericidal/permeability-increasing factor (BPI), a protein stored in neutrophils, and the acute phase protein LPS-binding protein (LBP) bind to LPS; however, BPI inhibits while LBP enhances binding of LPS to leukocytes and subsequent induction of cytokines. We investigated plasma levels of BPI, LBP, elastase and C5a before, during and after hemodialysis (HD). Six patients were dialysed with Cuprophane (Cup) and polysulfone (PS) low-flux dialyzers on two consecutive HD sessions. There was a significant, 10.9 +/- 2.8-fold increase in BPI after 4-hour HD compared to predialysis and a 4.4 +/- 1.6-fold increase in elastase after 4-hour HD using Cup. Plasma levels of BPI and elastase decreased rapidly after the dialysis session. HD with PS resulted in a smaller, but still significant rise in BPI (3.7 +/- 1.6-fold at 4 hours) and elastase (1.69 +/- 0.2-fold at 4 hours). Levels for BPI and elastase were similar in the arterial and venous blood lines of the dialyzer. Plasma levels of LBP did not change during or after the HD session. These data indicate that BPI, but not LBP is released during HD with Cup and to a lesser extent with PS. Activation of neutrophils and release of BPI during HD may influence the biological response to bacterial products possibly introduced during HD.

Acute-Phase Proteins↗

PubMed1993

Increase in prostanoid formation in rat liver macrophages (Kupffer cells) by human anaphylatoxin C3a.

Human anaphylatoxin C3a increases glycogenolysis in perfused rat liver. This action is inhibited by prostanoid synthesis inhibitors and prostanoid antagonists. Because prostanoids but not anaphylatoxin C3a can increase glycogenolysis in hepatocytes, it has been proposed that prostanoid formation in nonparenchymal cells represents an important step in the C3a-dependent increase in hepatic glycogenolysis. This study shows that (a) human anaphylatoxin C3a (0.1 to 10 micrograms/ml) dose-dependently increased prostaglandin D2, thromboxane B2 and prostaglandin F2 alpha formation in rat liver macrophages (Kupffer cells); (b) the C3a-mediated increase in prostanoid formation was maximal after 2 min and showed tachyphylaxis; and (c) the C3a-elicited prostanoid formation could be inhibited specifically by preincubation of C3a with carboxypeptidase B to remove the essential C-terminal arginine or by preincubation of C3a with Fab fragments of a neutralizing monoclonal antibody. These data support the hypothesis that the C3a-dependent activation of hepatic glycogenolysis is mediated by way of a C3a-induced prostanoid production in Kupffer cells.

Animals↗

PubMed1992

Binding of fluorescein-labeled anaphylatoxin C5a to human peripheral blood, spleen, and bone marrow leukocytes.

The expression of C5a receptors (C5aR) on human leukocytes was evaluated by flow cytometry using fluorescein-labeled human C5a (C5a-F). Granulocytes and CD14+ mononuclear cells (MNL) but not CD3+, CD20+, CD16+, CD56+, or CD11b+ lymphocytes in peripheral blood and spleen bound C5a-F. C5a-F binding was saturable and inhibitable by anti-C5a monoclonal antibody (MoAb) C17/5 or unlabeled C5a. During hemodialysis, which led to the generation of C5a, only granulocytes and monocytes increased their expression of the adhesion molecule CD11b (CR3). In vitro, C5a induced an increase of CR3 and p 150/95 (CD11c/CR4) only on myeloid cells. However, treatment of leukocytes with phorbol 12-myristate 13 acetate increased CR3 and CR4 expression on both myeloid cells and a lymphocyte subpopulation. Stimulation of MNL in mixed lymphocyte cultures or by treatment with conditioned medium or with IFN-gamma did not induce binding sites for C5aR on lymphocytes and reduced the binding of C5a-F to monocytes. The expression of C5aR on low-density bone marrow cells was analyzed by setting appropriate gates during flow cytometry. Cells that bound C5a-F were found in all populations that contained granulocyte and monocyte precursors, but not in lymphocyte precursor populations. All C5aR+ bone marrow cells were CD34 and expressed high levels of CR3, which suggests a late appearance of C5aR during myeloid cell maturation. Our results indicate that C5aR is exclusively expressed on myeloid cells within the hematopoetic cell population.

Antibodies, Monoclonal↗

PubMed1991

Differential effects of human anaphylatoxin C3a on glucose output and flow in rat liver during orthograde and retrograde perfusion: the periportal scavenger cell hypothesis.

1) During orthograde perfusion of rat liver human anaphylatoxin C3a caused an increase in glucose and lactate output and reduction of flow. These effects could be enhanced nearly twofold by co-infusion of the carboxypeptidase inhibitor MERGETPA, which reduced inactivation of C3a to C3adesArg. 2) During retrograde perfusion C3a caused a two- to threefold larger increase in glucose and lactate output and reduction of flow than in orthograde perfusions. These actions tended to be slightly enhanced by MERGETPA. 3) The elimination of C3a plus C3adesArg immunoreactivity during a single liver passage was around 67%, irrespective of the perfusion direction and the presence of the carboxypeptidase inhibitor MERGETPA; however, less C3adesArg and more intact C3a appeared in the perfusate in the presence of MERGETPA in orthograde and retrogade perfusions. It is concluded that rat liver inactivated human anaphylatoxin C3a by conversion to C3adesArg and moreover eliminated it by an additional process. The inactivation to C3adesArg seemed to be located predominantly in the proximal periportal region of the liver sinusoid, since C3a was less effective in orthograde perfusions, when C3a first passed the proximal periportal region before reaching the predominant mass of parenchyma as its site of action, than in retrograde perfusions, when it first passed the perivenous area. These data may be evidence for a periportal scavenger mechanism, by which the liver protects itself from systemically released mediators of inflammation that interfere with the local regulation of liver metabolism and hemodynamics.

3-Mercaptopropionic Acid↗