Function Of Cr3 Research Articles

Effect of Cr3+ doping concentration on the microstructure, mechanical properties and optical properties of Cr3+: SrF2 transparent ceramics

Cr3+: SrF2 nanopowders were synthesized using a chemical co-precipitation method. The nanoparticles exhibited a structure consistent with the pure SrF2 phase. Cr3+: SrF2 transparent ceramics were fabricated by hot-pressed (HP) sintering technique. The transmittance of 1 at% Cr3+: SrF2 transparent ceramics reached up to 83 % at 1054 nm, which is superior to other SrF2 transparent ceramics with different Cr3+ doping concentration. Furthermore, the mechanical properties of Cr3+: SrF2 transparent ceramics improved with increasing Cr3+ doping levels. The 1 at% Cr3+: SrF2 transparent ceramics exhibited the best mechanical properties, with a microhardness of 2.573 GPa, fracture toughness of 0.70 MPa·m1/2, and compressive strength of 38.1 MPa. The luminescence spectra and fluorescence lifetimes of the SrF2 transparent ceramics as a function of Cr3+ doping concentration were also analyzed and discussed.

Low-frequency inherited complement receptor variants are associated with purpura fulminans

AbstractExtreme disease phenotypes can provide key insights into the pathophysiology of common conditions, but studying such cases is challenging due to their rarity and the limited statistical power of existing methods. Herein, we used a novel approach to pathway–based mutational burden testing, the rare variant trend test (RVTT), to investigate genetic risk factors for an extreme form of sepsis-induced coagulopathy, infectious purpura fulminans (PF). In addition to prospective patient sample collection, we electronically screened over 10.4 million medical records from 4 large hospital systems and identified historical cases of PF for which archived specimens were available to perform germline whole-exome sequencing. We found a significantly increased burden of low-frequency, putatively function-altering variants in the complement system in patients with PF compared with unselected patients with sepsis (P = .01). A multivariable logistic regression analysis found that the number of complement system variants per patient was independently associated with PF after controlling for age, sex, and disease acuity (P = .01). Functional characterization of PF-associated variants in the immunomodulatory complement receptors CR3 and CR4 revealed that they result in partial or complete loss of anti-inflammatory CR3 function and/or gain of proinflammatory CR4 function. Taken together, these findings suggest that inherited defects in CR3 and CR4 predispose to the maladaptive hyperinflammation that characterizes severe sepsis with coagulopathy.

Effect of Cr cations addition on the structural, morphological, optical, and photocatalytic properties of Er-doped ZnO structures

In this work, we have investigated the effect of Cr3+ cations addition on the structural, morphological, optical, and photocatalytic properties of Er-doped ZnO structures. The Zn(1-(x-y))ErxCryO compound, where [(x; y) = (0.00; 0.00), (0.02; 0.01), (0.02; 0.02) and (0.02; 0.03)] was synthesized by the co-precipitation method and thermally treated at 100 °C for 6 h. The structural study showed that the dopant cations concentrations, cause variations in lattice constants, and increase the crystallite size and the strain in the ZnO crystal lattice. The structural atomic disorder was confirmed by Raman and photoluminescence spectroscopies, with VO, VO+, and VO++ type oxygen vacancy defects dominating. The samples exhibited different morphologies depending on the dopant concentration (plates-like, irregular hemispherical particles, and octahedrons-like structures). In the photocatalytic test, the methylene blue (MB) dye degradation under UV irradiation increased as a function of Cr3+ cations concentration, achieving a degradation rate of 37.4 ± 1.9% for the sample containing 2% of Er3+ cations and 3% of Cr3+ cations. In addition, the MB dye removal capacity by the Zn(1-(x-y))ErxCryO compound was incremented to above 85% using an optimized H2O2 concentration. Finally, the irradiated solution did not show toxicity against Artemia salina, indicating that the intermediate photoproducts formed are not toxic.

Spectral Broadening in Cr3+-Doped Sr0.92Mg0.91Al10.1O17 NIR Phosphor Realized by Multi-crystallographic Site Occupation

Near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs) play an important role in nondestructive testing, medical imaging, food analysis, and so on. Broadband NIR phosphors are needed in order to cover the characteristic wavelengths of various matters. In this paper, a NIR phosphor, Sr0.92Mg0.91Al10.1O17 (SMAO):Cr3+, with a full width at half maximum (FWHM) of 12–102 nm is achieved as a function of Cr3+ concentration. Two Cr3+ sites are observed by means of excitation spectra and fluorescence decay curves. The spectral broadening with the increase of Cr3+ concentration is attributed to the increase of occupation ratio on the weak crystal field site by Cr3+. In addition, the difference in thermal stability between 2E and 4T2 is employed to conduct the temperature measurement with a relative sensitivity of 0.43% K–1 at 270 K. A NIR pc-LED is fabricated using SMAO:0.03Cr3+ phosphor combined with a 395 nm LED chip with radiation flux of 2.2 mW@10 mA and 15 mW@100 mA.

Conserved regions of the regulatory subunit Spo7 are required for Nem1–Spo7/Pah1 phosphatase cascade function in yeast lipid synthesis

In the yeast Saccharomyces cerevisiae, the Nem1-Spo7 complex is a protein phosphatase that activates Pah1 phosphatidate phosphatase at the nuclear-endoplasmic reticulum membrane for the synthesis of triacylglycerol. The Nem1-Spo7/Pah1 phosphatase cascade largely controls whether phosphatidate is partitioned into the storage lipid triacylglycerol or into membrane phospholipids. The regulated synthesis of the lipids is crucial for diverse physiological processes during cell growth. Spo7 in the protein phosphatase complex is required as a regulatory subunit for the Nem1 catalytic subunit to dephosphorylate Pah1. The regulatory subunit contains three conserved homology regions (CR1, CR2, and CR3). Previous work showed that the hydrophobicity of LLI (residues 54-56) within CR1 is important for Spo7 function in the Nem1-Spo7/Pah1 phosphatase cascade. In this work, by deletion and site-specific mutational analyses, we revealed that CR2 and CR3 are also required for Spo7 function. Mutations in any one of the conserved regions were sufficient to disrupt the function of the Nem1-Spo7 complex. We determined that the uncharged hydrophilicity of STN (residues 141-143) within CR2 was required for Nem1-Spo7 complex formation. In addition, the hydrophobicity of LL (residues 217 and 219) within CR3 was important for Spo7 stability, which indirectly affected complex formation. Finally, we showed the loss of Spo7 CR2 or CR3 function by the phenotypes (e.g., reduced amounts of triacylglycerol and lipid droplets, temperature sensitivity) that are attributed to defects in membrane translocation and dephosphorylation of Pah1 by the Nem1-Spo7 complex. These findings advance knowledge of the Nem1-Spo7 complex and its role in lipid synthesis regulation.

Two-dimentional photo-thermo-polimerisation of MMA with Cr3+ doped nanoheaters

Through a wise design of materials composition and chemical architecture, modern functional nanomaterials should offer enhanced properties and multifunctional capabilities. This is why new photothermal agents are sought that not only are efficient in light-to-heat conversion but advance other functionalities such as luminescence based sensing that assure feedback control or thermal triggering / activation of (bio)chemical processes. In this work YPO4:Cr3+ nanoparticles are presented and their photothermal performance is evaluated as a function of Cr3+ ions concentration. As demonstrated, the high absorption cross-section of Cr3+ ions causes that despite the light-to-heat conversion efficiency for CrPO4 reached only 15% the temperature raises obtained with optical excitation of 4.3 kW/cm2 is 250% higher for CrPO4 compared to NaNdF4 nanoparticles. The high application potential of the presented photothermal agents was demonstrated in an experiment with dynamic photo-thermo-polymerization of MMA that can be used for 3D printing.

Analysis of E1A domains involved in the enhancement of CDK2 activity

E1A is an adenoviral protein which is expressed at the early phase after viral infection and contains four conserved regions (CR1, CR2, CR3 and CR4). Our previous work suggests that E1A facilitates the formation of cyclin A-CDK2 complex and thereby enhances CDK2 activity. However, the molecular function of E1A in CDK2 activation has been unclear. Here, we studied the mechanism of enhancement of CDK2 activity by E1A, using the E1A variant forms which selectively contain CR domains. We isolated four E1A variant forms, i.e. 13S (containing CR1, CR2, CR3, CR4), 12S (CR1, CR2, CR4), 10S (CR2, CR4) and 9S (CR4), derived from HEK293 cells which express E1A. 13S promoted G2/M-phase arrest, upon CDK2 hyper-activation by co-expressing a stabilized cyclin A mutant, most strongly among those E1A variant forms. Concomitantly, the specific activity of the 13S-associated CDK2 was highest among them. 10S exhibited lower affinity for CDK2 than the 13S while the affinity for CDK2 was comparable between 13S and 12S. Nonetheless, 12S did not enhance the CDK2 specific activity. On the other hand, a mutation in CR2 domain, which is essential for binding to p107, suppressed both the binding and activation of CDK2. These results suggest that CR1 domain, in addition to CR2 domain via p107 interaction, is important for binding to CycA-CDK2 complex while CR3 domain facilitates CDK2 activation. Since the function of CR3 in cell cycle regulation has been relatively unknown, we propose the enhancement of CDK2 activity as a novel function of CR3 domain.

Capsule carbohydrate structure determines virulence in Acinetobacter baumannii.

Acinetobacter baumannii is a highly antibiotic-resistant bacterial pathogen for which novel therapeutic approaches are needed. Unfortunately, the drivers of virulence in A. baumannii remain uncertain. By comparing genomes among a panel of A. baumannii strains we identified a specific gene variation in the capsule locus that correlated with altered virulence. While less virulent strains possessed the intact gene gtr6, a hypervirulent clinical isolate contained a spontaneous transposon insertion in the same gene, resulting in the loss of a branchpoint in capsular carbohydrate structure. By constructing isogenic gtr6 mutants, we confirmed that gtr6-disrupted strains were protected from phagocytosis in vitro and displayed higher bacterial burden and lethality in vivo. Gtr6+ strains were phagocytized more readily and caused lower bacterial burden and no clinical illness in vivo. We found that the CR3 receptor mediated phagocytosis of gtr6+, but not gtr6-, strains in a complement-dependent manner. Furthermore, hypovirulent gtr6+ strains demonstrated increased virulence in vivo when CR3 function was abrogated. In summary, loss-of-function in a single capsule assembly gene dramatically altered virulence by inhibiting complement deposition and recognition by phagocytes across multiple A. baumannii strains. Thus, capsular structure can determine virulence among A. baumannii strains by altering bacterial interactions with host complement-mediated opsonophagocytosis.

The differential role of CR3 (CD11b/CD18) and CR4 (CD11c/CD18) in the adherence, migration and podosome formation of human macrophages and dendritic cells under inflammatory conditions.

CR3 and CR4, the leukocyte specific β2-integrins, involved in cellular adherence, migration and phagocytosis, are often assumed to have similar functions. Previously however, we proved that under physiological conditions CR4 is dominant in the adhesion to fibrinogen of human monocyte-derived macrophages (MDMs) and dendritic cells (MDDCs). Here, using inflammatory conditions, we provide further evidence that the expression and function of CR3 and CR4 are not identical in these cell types. We found that LPS treatment changes their expression differently on MDMs and MDDCs, suggesting a cell type specific regulation. Using mAb24, specific for the high affinity conformation of CD18, we proved that the activation and recycling of β2-integrins is significantly enhanced upon LPS treatment. Adherence to fibrinogen was assessed by two fundamentally different approaches: a classical adhesion assay and a computer-controlled micropipette, capable of measuring adhesion strength. While both receptors participated in adhesion, we demonstrated that CR4 exerts a dominant role in the strong attachment of MDDCs. Studying the formation of podosomes we found that MDMs retain podosome formation after LPS activation, whereas MDDCs lose this ability, resulting in a significantly reduced adhesion force and an altered cellular distribution of CR3 and CR4. Our results suggest that inflammatory conditions reshape differentially the expression and role of CR3 and CR4 in macrophages and dendritic cells.

First-principle study of the microstructure and electronic properties for Cr3+ doped yttrium orthoaluminate

Chromium ion (Cr3+) doped YAlO3 host crystal shows strong prospects for the exploitation of new optical materials. However, the microstructure of Cr3+ doped of YAlO3 is still unclear. In this work, we systematically explore the structural evolutions of Cr3+ doped of YAlO3 system by using the CALYPSO method and density functional theory. A novel cage-like structure with P-1 space group is identified for the first time. The impurity Cr3+ ion can naturally substitute the Al3+ ion of the central site in the crystal lattice. The result show that the impurity Cr3+ concentration is determined to be 6.25%, which is almost comparable to the experiments. The perfect agreement between our simulated X-ray diffraction patterns and the measured ones demonstrates the validity of the ground-state structure. The calculation of electronic band structure for Cr3+ doped YAlO3 reveals a closure of the insulator band gap, forming an energy gap of 2.94 eV. The result of electronic density of states shows that it is the impurity Cr3+ ion that leads to a transition from insulator to semiconductor. By analyzing the electron localization function of Cr3+ doped of YAlO3 crystal, we conclude that the Cr–O interaction is dominantly ionic bond. The obtained results could provide an important understanding of the transition-metal doped host materials.

Solvent effect on the formation of active free radicals from H2O2 catalyzed by Cr-substituted PKU-1 aluminoborate: Spectroscopic investigation and reaction mechanism

The nature of a solvent plays an important role in selectively catalytic oxidations, influencing the catalytic activity and product selectivity. Most work attribute such roles to the polarity, acidity/basicity, or coordination ability of the solvent. Here, we systematically investigated the generated active free radicals in five different organic solvents during the catalytic oxidation of styrene by H2O2. Cr-doped PKU-1 aluminoborate was selected as the heterogeneous catalyst in this system. The solvent effect was comprehensively understood along this perspective. Hydroxyl radicals (OH) were preferred to be formed in CH3CN and responsible for the formation of carbonyl compounds, while superoxide ion radicals (O2−) were favored in DMF and beneficial to the epoxide production. The function of Cr3+ was correlated with the solvent effect and a tentative mechanism pathway was proposed accordingly.

The complement receptor 3 (CD11b/CD18) agonist Leukadherin-1 suppresses human innate inflammatory signalling.

SummaryComplement receptor 3 (CR3, CD11b/CD18) is a multi‐functional receptor expressed predominantly on myeloid and natural killer (NK) cells. The R77H variant of CD11b, encoded by the ITGAM rs1143679 polymorphism, is associated robustly with development of the autoimmune disease systemic lupus erythematosus (SLE) and impairs CR3 function, including its regulatory role on monocyte immune signalling. The role of CR3 in NK cell function is unknown. Leukadherin‐1 is a specific small‐molecule CR3 agonist that has shown therapeutic promise in animal models of vascular injury and inflammation. We show that Leukadherin‐1 pretreatment reduces secretion of interferon (IFN)‐γ, tumour necrosis factor (TNF) and macrophage inflammatory protein (MIP)‐1β by monokine‐stimulated NK cells. It was associated with a reduction in phosphorylated signal transducer and activator of transcription (pSTAT)‐5 following interleukin (IL)‐12 + IL‐15 stimulation (P < 0·02) and increased IL‐10 secretion following IL‐12 + IL‐18 stimulation (P < 0·001). Leukadherin‐1 pretreatment also reduces secretion of IL‐1β, IL‐6 and TNF by Toll‐like receptor (TLR)‐2 and TLR‐7/8‐stimulated monocytes (P < 0·01 for all). The R77H variant did not affect NK cell response to Leukadherin‐1 using ex‐vivo cells from homozygous donors; nor did the variant influence CR3 expression by these cell types, in contrast to a recent report. These data extend our understanding of CR3 biology by demonstrating that activation potently modifies innate immune inflammatory signalling, including a previously undocumented role in NK cell function. We discuss the potential relevance of this to the pathogenesis of SLE. Leukadherin‐1 appears to mediate its anti‐inflammatory effect irrespective of the SLE‐risk genotype of CR3, providing further evidence to support its evaluation of Leukadherin‐1 as a potential therapeutic for autoimmune disease.

Magnetic Hysteresis and Complex Initial Permeability of Cr&amp;lt;sup&amp;gt;3+&amp;lt;/sup&amp;gt; Substituted Mn-Zn Ferrites

The impact of Cr3+ ion on the magnetic properties of Mn0.50Zn0.50CrxFe2-xO4 (with x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5) has been studied. Ferrite samples were synthesized by combustion method and sintered at various temperatures (1250°C, 1300°C and 1350°C). The structural properties were investigated by means of X-ray diffraction patterns and indicated that the samples possess single phase cubic spinel structure. The lattice parameter decreases with the increase in Cr3+ content, as the ionic radius of Cr3+ ion is smaller than that of Fe3+. The average grain size (D), bulk density (ρB) and initial permeability （μi’ ）decreases with increase in Cr3+ content whereas porosity follows its opposite trend. The ρB was found to increase with increase in Cr3+ content as the sintering temperature (Ts) is increased from 1250°C to 1350°C. The Ts affects the densification, grain growth and （μi’ ） of the samples. The （μi’ ） strongly depends on average grain size, density and intragranular porosity. The B-H loops of the compositions were measured at room temperature. The saturation magnetization (Ms), coercivity (Hc) and hysteresis losses were studied as a function of Cr3+ content. The Ms was found to decrease with the increase of Cr3+ content, which is attributed to the dilution of A-B interaction.

Development of a chromium speciation probe based on morphology-dependent aggregation of polymerized vesicle-functionalized gold nanoparticles

In this work, a new approach for visual sensing of Cr3+ in aqueous solutions is presented, based on the morphological changes induced by Cr3+ on (4-carboxybenzyl)bis[2-(undec-10-enyloxycarbonyl)ethyl]methylammonium bromide (4-CBUAB)-polymerized vesicles. CTAB-stabilized gold nanoparticles (GNPs) react with 4-CBUAB-polymerized vesicles to form aggregates via vesicle-micelle interactions, which does not proceed further because of vesicle-vesicle repulsive forces, creating a large polymerized vesicle-gold nanoparticle (PV-GNP) conjugate. The incorporation of Cr3+ through the 4-CBUAB polymeric membrane induces structural perturbations on the polymerized vesicle morphology by swelling of the lamellar phase which is reflected in the morphology of the polymerized vesicle-gold nanoparticle conjugate assembly. These steric perturbations induce a linear increase in the absorbance of the solutions as a function of Cr3+ concentration, a feature which was exploited for the analytical determination of Cr3+ in real samples. Owing to the high selectivity of the polymerized vesicular aggregate no interferences from co-existing species were observed, enabling the determination and speciation of Cr3+ in real samples with minimal sample pre-treatment and without preconcentration. The analytical merits afford detection limits as low as 0.72 microg L(-1) by extracting only 5 mL of sample volume with satisfactory reproducibility (RSD = 5.21%, C = 10 microg L(-1), n = 6), which are directly comparable to those attained with more sophisticated techniques.

CR1 (CD35) and CR3 (CD11b/CD18) mediate infection of human monocytes and monocytic cell lines with complement-opsonized HIV independently of CD4.

Peripheral blood and tissue mononuclear phagocytes serve as major viral reservoirs in HIV-infected individuals. We investigated the role of complement receptors CR1 (CD35) and CR3 (CD11b/CD18) in mediating productive infection with complement-opsonized HIV-1 and HIV-2 of cultured normal human peripheral blood monocytes, the promonocytic cell line THP-1, the monocytic cell line Mono Mac 6 and the glial cell line U251-MG. Cells were infected with the HTLV-IIIB strain of HIV-1 or the LAV-2 strain of HIV-2 that had been preopsonized with fresh human normal HIV seronegative serum. Productive infection was assessed by syncytia formation, the MTT cytotoxicity assay and/or release of p24 antigen in culture supernatants. Using suboptimal amounts of virus to infect the cells, we observed a higher and earlier productive infection of the cells with complement-opsonized HIV than with unopsonized virus. The enhancing effect of complement was totally suppressed by blocking CR1 or CR3 function with F(ab)'2 fragments of anti-receptor MoAbs; while blocking of the LFA-1 antigen had no effect. The infection of monocytic cells with complement-opsonized virus occurred independently of CD4 since it was not inhibited by F(ab)'2 fragments of a MoAb against the gp120 binding site of CD4 and since infection also occurred with Mono Mac 6 and U251-MG cells, which lack expression of the CD4 antigen and of CD4 mRNA. These observations suggest that complement may mediate productive infection of cells of the monocytic lineage with 'lymphocytotropic' HIV strains independently of CD4.

Influence of CR3 (CD11b/CD18) Expression on Phagocytosis ofBordetella pertussisby Human Neutrophils

CR3 (CD11b/CD18) is expressed on neutrophils, and the engagement of CR3 can promote phagocytosis. CR3 serves as the receptor for the Bordetella pertussis adhesin filamentous hemagglutinin (FHA) and for the adenylate cyclase toxin (ACT), which blocks neutrophil function. The influence of CR3, FHA, and ACT on the phagocytosis of B. pertussis by human neutrophils was examined. The surface expression and function of CR3 are regulated. Tumor necrosis factor alpha (TNF-alpha) and gamma interferon (IFN-gamma) increased CR3 surface expression, but only TNF-alpha increased the ability of neutrophils to phagocytose B. pertussis, suggesting that elevated CR3 expression alone is not sufficient to promote phagocytosis. Purified FHA and pertussis toxin also increased the surface expression of CR3 on neutrophils, while ACT and the B subunit of pertussis toxin did not affect CR3 expression. FHA-mediated attachment to CR3 can lead to phagocytosis, especially in the absence of ACT. FHA mutants failed to attach and were not phagocytosed by neutrophils. Similarly, an antibody to CR3 blocked both attachment and phagocytosis. The addition of exogenous FHA enhanced the attachment and phagocytosis of wild-type B. pertussis and FHA mutants. Mutants lacking the SphB1 protease, which cleaves FHA and allows the release of FHA from the bacterial surface, were phagocytosed more efficiently than wild-type bacteria. ACT mutants were efficiently phagocytosed, but wild-type B. pertussis or ACT mutants plus exogenous ACT resisted phagocytosis. These studies suggest that the activation and surface expression of CR3, FHA expression, and the efficiency of ACT internalization all influence whether B. pertussis will be phagocytosed and ultimately killed by neutrophils.

A mixed population of immature and mature leucocytes in umbilical cord blood results in a reduced expression and function of CR3 (CD11b/CD18).

Neonatal neutrophils express less membrane and cytoplasmic CR3 (iC3b-receptor, Mac-1, alphaM beta2-integrin) than do adult neutrophils, and it has been suggested that this renders neonatal neutrophils deficient in diapedesis and bactericidal activity. The reason(s) for this deficiency are unknown. In this study, CR3 expression and the CR3-dependent respiratory burst activity of individual neonatal neutrophils are quantified in comparison with adult leucocytes using flow cytometry. Monocytes and neutrophils are defined as CD14highCD15low and CD14lowCD15high, respectively. Although neonatal neutrophils bore less CR3 on average than did adult neutrophils, neonatal neutrophils were more heterogeneous and many neonatal neutrophils expressed adult levels of CR3. Because of higher neutrophil concentrations in cord versus adult blood, the calculated number of neutrophils in cord blood expressing high amounts of CR3 was equivalent to that of adult blood. Similar findings were made with monocytes. The size of the CR3-dependent respiratory burst stimulated by particulate beta-glucan correlated directly with the expression of CR3 by individual neutrophils. With neonatal and adult neutrophils having comparable CR3 densities, the respiratory burst activities were equivalent. Wright-Giemsa differential staining of the subset of neonatal neutrophils with low CR3 levels isolated by fluorescence-activated cell sorting showed a higher proportion of immature cells than the sorted population expressing high CR3 levels. Therefore, higher proportions of immature cells in cord blood probably explain previous reports of deficient CR3 expression and function. The typical neutrophilia of cord blood may compensate for this apparent deficiency by providing adult concentrations of mature neutrophils.

Effect of mycobacterial phospholipids on interaction of Mycobacterium tuberculosis with macrophages.

This study demonstrates that pretreatment of macrophages with phosphatidylinositol, of either soya bean or mycobacterial origin, results in a down-regulation of the binding and uptake of Mycobacterium tuberculosis by the phagocytes. We also describe the novel observation that cardiolipin induces an increase in the binding and uptake of M. tuberculosis by macrophages. Neither phospholipid interacts with macrophages via the 2F8 epitope of scavenger receptor A, and treatment of macrophages with either phospholipid results in a down-regulation of CR3 function and tumor necrosis factor alpha production by the phagocyte. We have also shown that the ability of macrophages to interact with mycobacteria is greatly affected by an as yet unidentified product from the interaction of chloroform and polypropylene tubes.

Critical role of Kupffer cell CR3 (CD11b/CD18) in the clearance of IgM-opsonized erythrocytes or soluble β-glucan

Liver macrophages (Kupffer cells) play a major role in blood clearance of both C3-opsonized immune complexes and therapeutic β-glucan polysaccharides. Human Kupffer cells express three types of C3-receptors: CR1 (C3b-receptor; CD35), CR3 (iC3b- and β-glucan-receptor), and CR4 (iC3b-receptor; CD11c/CD18). Studies of isolated macrophages have suggested that CR3 is the major receptor mediating capture of either C3-opsonized erythrocytes (E) or β-glucans. In this investigation, the organ distribution and function of CR3 in the clearance of IgM-opsonized E and soluble CR3-binding polysaccharides were explored in normal vs. CR3-knockout (CR3-KO) mice. Analysis of intravenously (i.v.) injected 125I-anti-CR3 showed that the major vascular reservoir of CR3 was the liver, followed by spleen and lungs. By contrast, clearance of 125I-anti-CR1 appeared to be mediated predominantly by splenic B lymphocytes, as only subsets of splenic macrophages or Kupffer cells were found to express CR1. Clearance of IgM-opsonized 51Cr-E occurred rapidly to the livers of normal mice but was nearly absent in CR3-KO mice. Soluble 125I-β-glucan exhibited rapid clearance to the liver in normal mice, whereas clearance in CR3-KO mice was significantly reduced. In conclusion, Kupffer cell CR3 plays a crucial role in the clearance of both IgM-opsonized E and β-glucans.

Thermodynamic and statistical studies of supersaturated ternary solutions.

The influence of chromium ions Cr3+ on properties of supersaturated aqueous solution of ammonium sulfate (NH4)2SO4 has been studied employing containerless electrodynamic levitation of single microdroplets of this solution with known concentration of Cr3+ ions. The water activity versus solute concentration was measured in three different sets of experiments corresponding to different initial concentrations of Cr3+ ions. Theoretical treatment of the experimental results obtained is developed employing the theory of supersaturated electrolyte solutions [Phys. Rev. E 52, 1325 (1995)]. This treatment has allowed the following two conclusions. First, spinodal concentration is a decreasing function of Cr3+ concentration. Second, solute clusters formed in the presence of Cr3+ ions demonstrate complex behavior with respect to binding water molecules: (a) at low and moderate supersaturations, they bind more water molecules than clusters formed in the absence of an impurity; and (b) at high supersaturations, they bind less water molecules than clusters formed in the absence of an impurity.