Interaction of antibodies with renal cell surface antigens

Over the past ten years it has been increasingly recognized that immune complex nephritides, characterized by the accumulation of granular immune deposits in renal structures, may not only be the consequence of deposition of circulating immune complexes but also of antigen-antibody complexes aggregated locally or formed in situ [1]. One of the sites at which antibodies may interact locally with antigens in the kidney is at the surface of renal cells [1, 2]. There is an abundance of antigens on cells: part of them are intrinsic plasma membrane proteins, while others may be present because they are secretion products or they have been ‘planted“ on the cell surface for immunological or physico-chemical reasons. In this article renal lesions that may arise from the binding of antibodies with these various kinds of cell surface antigens will be reviewed. Most of our insights come from animal models of renal disease. In the closing section the potential impact of data derived from experimental pathology on our concepts of human nephropathies will be evaluated

Wavelet-based Faraday Rotation Measure Synthesis

Faraday Rotation Measure (RM) Synthesis, as a method for analyzing multi-channel observations of polarized radio emission to investigate galactic magnetic fields structures, requires the definition of complex polarized intensity in the range of the negative lambda square. We introduce a simple method for continuation of the observed complex polarized intensity into this domain using symmetry arguments. The method is suggested in context of magnetic field recognition in galactic disks where the magnetic field is supposed to have a maximum in the equatorial plane. The method is quite simple when applied to a single Faraday-rotating structure on the line of sight. Recognition of several structures on the same line of sight requires a more sophisticated technique. We also introduce a wavelet-based algorithm which allows us to consider a set of isolated structures. The method essentially improves the possibilities for reconstruction of complicated Faraday structures using the capabilities of modern radio telescopes.Comment: 5 pages, 5 figures, accepted for publication in MNRAS Letter

Faraday caustics: Singularities in the Faraday spectrum and their utility as probes of magnetic field properties

We describe singularities in the distribution of polarized intensity as a function of Faraday depth (i.e. the Faraday spectrum) caused by line-of-sight (LOS) magnetic field reversals. We call these features Faraday caustics because of their similarity to optical caustics. They appear as sharply peaked and asymmetric profiles in the Faraday spectrum, that have a tail that extends to one side. The direction in which the tail extends depends on the way in which the LOS magnetic field reversal occurs (either changing from oncoming to retreating or vice versa). We describe how Faraday caustics will form three-dimensional surfaces that relate to boundaries between regions where the LOS magnetic field has opposite polarity. We present examples from simulations of the predicted polarized synchrotron emission from the Milky Way. We derive either the probability or luminosity distribution of Faraday caustics produced in a Gaussian magnetic field distribution as a function of their strength, F, and find that for strong Faraday caustics P(F)\proptoF^{-3} . If fully resolved, this distribution is also shown to depend on the Taylor microscale, which relates to the largest scale over which dissipation is important in a turbulent flow.Comment: 14 pages, 9 figures, Accepted for publication in Astronomy & Astrophysic

Relationship of kidney function to immunopathology in chronic serum sickness of rats

Relationship of kidney function to immunopathology in chronic serum sickness of rats. This study sought to clarify the relationship between kidney function and immunopathology in chronic serum sickness (CSS) of rats. CSS was induced by chronic intravenous immunization with bovine serum albumin. Whole kidney function was studied during the course of CSS by assays of serum and urine. Single nephron function was evaluated by micropuncture techniques. Three categories (mild, moderate, severe) ofkidney disease were identified from the analysis of kidney function in rats with CSS. Those categories represented distinct stages in the natural history of CSS nephritis. The three stages identified by measurements of function corresponded to distinct categories of kidney immunopathology. In rats with mild CSS, immune deposits were limited to the mesangium; histopathology was slight or absent. The only detectable change in protein handling was a small elevation of albumin concentration in tubule fluid. Abnormal proteinuria was a feature of moderate CSS; whole kidney glomerular filtration was not decreased despite evidence of significant immunopathology of glomeruli. Compromise of whole kidney function including decreased sodium excretion was only detected in the severe stage of CSS in association with diffuse proliferative glomerulonephritis. The transitions from mild to moderate and moderate to severe CSS were not gradual but occurred as discrete, sudden events.Relations entre la fonction rénale et l'immunopathologie au cours de la maladie sérique chronique chez des rats. Cette étude est destinée à clarifier la relation entre la fonction rénale et l'immunopathologie au cours de la maladie sérique chronique (CSS) chez des rats. CSS était induite par immunisation chronique intra-veineuse avec de la sérum albumine bovine. La fonction rénale globale était étudiée pendant la CSS par des dosages sériques et urinaires. La fonction rénale individuelle était évaluée par des techniques de microponction. Trois catégories (bénigne, modérée, sévère) de maladies rénales ont été identifiées à partir de l'analyse de la fonction rénale chez les rats atteints de CSS. Ces catégories représentaient des stades distincts de l'histoire naturelle de la néphrite de CSS. Les trois stades identifiés par les mesures des fonctions correspondaient à des catégories distinctes d'immunopathologie rénale. Chez les rats atteints de CSS bénigne, les dépôts immuns étaient limités au mésangium; l'histopathologic était minime ou absente. La seule modification détectable de la conservation des protéines était une élévation modéré de la concentration d'albumine dans le fluide tubulaire. Une protéinurie anormale était une caractéristique de la CSS modérée; la filtration glomérulaire globale n'était pas diminuée malgré l'existence d'une immunopathologie significative des glomérules. Une altération de la fonction rénale globale comprenant une diminution de l'excrétion sodée était détectée seulement au stade sévère de CSS, en association avec une glomérulonéphrite proliférative diffuse. Les passages de la forme bénigne à la forme modérée, et de la forme modérée à la forme sévère de CSS n'étaient pas progressifs, mais survennaient de façon tranchée, brutale

Distribution of basement membrane antigens in glomeruli of mice with autoimmune glomerulonephritis.

peer reviewedGlomerulonephritis was induced in mice by the repeated injection of human glomeruli or purified glomerular basement membrane. The glomerular basement membranes of nephritic animals were observed to develop subepithelial extensions, "spikes." Although normally Type IV collagen is found throughout the full thickness of basement membranes, the "spikes" reacted with antibodies to laminin but not with antibodies to Type IV collagen. It is proposed that in murine autoimmune glomerulonephritis, the visceral epithelial cells produce an excess of laminin

Identification of a target antigen in human anti-tubular basement membrane nephritis

Identification of a target antigen in human anti-tubular basement membrane nephritis. Sera from two patients with primary anti-tubular–basement–membrane–mediated tubulointerstitial nephritis, one a renal allograft recipient and the other with spontaneous anti-tubular–basement–membrane disease, were analyzed for the specificity of their autoantibodies. Both sera had circulating antibodies that reacted by ELISA with extracts of tubular basement membrane from several species, but failed to react significantly with extracts of glomerular basement membrane. Reactive antigen was solubilized with 6 M guanidine-HCl, 6 M urea, with reduction and alkylation, and with sodium dodecylsulfate. Digestion of the basement membrane with collagenase released relatively small quantities of antigen from the membrane, and trypsin and pepsin destroyed its antigenicity. The antigenic activity was characterized with respect to its size distribution by gel filtration and by immuno-overlay analysis of protein blots. Collectively, the results indicate that the major reactivity of both sera is directed towards a Mr 58,000 component that is unique to the tubular basement membrane. Minor reactivities toward high molecular weight components common to both glomerular and tubular basement membranes were detected by immuno-overlay analysis. This study identifies an antigen that is involved in human anti-tubular–basement–membrane–mediated tubulointerstitial nephritis, and demonstrates an advantage of the use of denaturing extraction over proteolytic methods to prepare the antigen

Faraday synthesis: The synergy of aperture and rotation measure synthesis

We introduce a new technique for imaging the polarized radio sky using interferometric data. The new approach, which we call Faraday synthesis, combines aperture and rotation measure synthesis imaging and deconvolution into a single algorithm. This has several inherent advantages over the traditional two-step technique, including improved sky plane resolution, fidelity, and dynamic range. In addition, the direct visibility- to Faraday-space imaging approach is a more sound foundation on which to build more sophisticated deconvolution or inference algorithms. For testing purposes, we have implemented a basic Faraday synthesis imaging software package including a three-dimensional CLEAN deconvolution algorithm. We compare the results of this new technique to those of the traditional approach using mock data. We find many artifacts in the images made using the traditional approach that are not present in the Faraday synthesis results. In all, we achieve a higher spatial resolution, an improvement in dynamic range of about 20%, and a more accurate reconstruction of low signal to noise source fluxes when using the Faraday synthesis technique.Comment: 11 pages, 5 figures, submitted to A&

Wide-field LOFAR-LBA power-spectra analyses: Impact of calibration, polarization leakage and ionosphere

Contamination due to foregrounds (Galactic and Extra-galactic), calibration errors and ionospheric effects pose major challenges in detection of the cosmic 21 cm signal in various Epoch of Reionization (EoR) experiments. We present the results of a pilot study of a field centered on 3C196 using LOFAR Low Band (56-70 MHz) observations, where we quantify various wide field and calibration effects such as gain errors, polarized foregrounds, and ionospheric effects. We observe a `pitchfork' structure in the 2D power spectrum of the polarized intensity in delay-baseline space, which leaks into the modes beyond the instrumental horizon (EoR/CD window). We show that this structure largely arises due to strong instrumental polarization leakage ($\sim30\%$) towards {Cas\,A} ($\sim21$ kJy at 81 MHz, brightest source in northern sky), which is far away from primary field of view. We measure an extremely small ionospheric diffractive scale ($r_{\text{diff}} \approx 430$ m at 60 MHz) towards {Cas\,A} resembling pure Kolmogorov turbulence compared to $r_{\text{diff}} \sim3 - 20$ km towards zenith at 150 MHz for typical ionospheric conditions. This is one of the smallest diffractive scales ever measured at these frequencies. Our work provides insights in understanding the nature of aforementioned effects and mitigating them in future Cosmic Dawn observations (e.g. with SKA-low and HERA) in the same frequency window.Comment: 20 pages, 11 figures, accepted for publication in MNRA

Galactic interstellar filaments as probed by LOFAR and Planck

Recent Low Frequency Array (LOFAR) observations at 115-175 MHz of a field at medium Galactic latitudes (centered at the bright quasar 3C196) have shown striking filamentary structures in polarization that extend over more than 4 degrees across the sky. In addition, the Planck satellite has released full sky maps of the dust emission in polarization at 353GHz. The LOFAR data resolve Faraday structures along the line of sight, whereas the Planck dust polarization maps probe the orientation of the sky projected magnetic field component. Hence, no apparent correlation between the two is expected. Here we report a surprising, yet clear, correlation between the filamentary structures, detected with LOFAR, and the magnetic field orientation, probed by the Planck satellite. This finding points to a common, yet unclear, physical origin of the two measurements in this specific area in the sky. A number of follow-up multi- frequency studies are proposed to shed light on this unexpected finding.Comment: 6 pages, 4 figures, accepted for publication in MNRAS Letter

Foregrounds for observations of the cosmological 21 cm line: II. Westerbork observations of the fields around 3C196 and the North Celestial Pole

In the coming years a new insight into galaxy formation and the thermal history of the Universe is expected to come from the detection of the highly redshifted cosmological 21 cm line. The cosmological 21 cm line signal is buried under Galactic and extragalactic foregrounds which are likely to be a few orders of magnitude brighter. Strategies and techniques for effective subtraction of these foreground sources require a detailed knowledge of their structure in both intensity and polarization on the relevant angular scales of 1-30 arcmin. We present results from observations conducted with the Westerbork telescope in the 140-160 MHz range with 2 arcmin resolution in two fields located at intermediate Galactic latitude, centred around the bright quasar 3C196 and the North Celestial Pole. They were observed with the purpose of characterizing the foreground properties in sky areas where actual observations of the cosmological 21 cm line could be carried out. The polarization data were analysed through the rotation measure synthesis technique. We have computed total intensity and polarization angular power spectra. Total intensity maps were carefully calibrated, reaching a high dynamic range, 150000:1 in the case of the 3C196 field. [abridged]Comment: 20 pages, 22 figures, accepted for publication in A&A. A version with full resolution figures is available at http://www.astro.rug.nl/~bernardi/NCP_3C196/bernardi.pd