Biomedical subjects

Bernd Kaspers

Publications and source records attributed to Bernd Kaspers.

17 recordsLinked to original sources

PubMed2007

Unique and conserved functions of B cell-activating factor of the TNF family (BAFF) in the chicken.

The chicken represents the best-characterized animal model for B cell development in the so-called gut-associated lymphoid tissue (GALT) and the molecular processes leading to B cell receptor diversification in this species are well investigated. However, the mechanisms regulating B cell development and homeostasis in GALT species are largely unknown. Here we investigate the role played by the avian homologue of B cell-activating factor of the tumor necrosis factor family (BAFF). Flow cytometric analysis showed that the receptor for chicken B cell-activating factor of the tumor necrosis factor family (chBAFF) is expressed by mature and immature B cells. Unlike murine and human BAFF, chBAFF is primarily produced by B cells both in peripheral lymphoid organs and in the bursa of Fabricius, the chicken's unique primary lymphoid organ. In vitro and in vivo studies revealed that chBAFF is required for mature B cell survival. In addition, in vivo neutralization with a decoy receptor led to a reduction of the size and number of B cell follicles in the bursa, demonstrating that, in contrast to humans and mice, in chickens BAFF is also required for the development of immature B cells. Collectively, we show that chBAFF has phylogenetically conserved functions in mature B cell homeostasis but displays unique and thus far unknown properties in the regulation of B cell development in birds.

Animals↗

PubMed2006

Identification and functional validation of novel autoantigens in equine uveitis.

The development, progression, and recurrence of autoimmune diseases are frequently driven by a group of participatory autoantigens. We identified and characterized novel autoantigens by analyzing the autoantibody binding pattern from horses affected by spontaneous equine recurrent uveitis to the retinal proteome. Cellular retinaldehyde-binding protein (cRALBP) had not been described previously as autoantigen, but subsequent characterization in equine recurrent uveitis horses revealed B and T cell autoreactivity to this protein and established a link to epitope spreading. We further immunized healthy rats and horses with cRALBP and observed uveitis in both species with typical tissue lesions at cRALBP expression sites. The autoantibody profiling outlined here could be used in various autoimmune diseases to detect autoantigens involved in the dynamic spreading cascade or serve as predictive markers.

Animals↗

PubMed2006

The avian lung-associated immune system: a review.

The lung is a major target organ for numerous viral and bacterial diseases of poultry. To control this constant threat birds have developed a highly organized lung-associated immune system. In this review the basic features of this system are described and their functional properties discussed. Most prominent in the avian lung is the bronchus-associated lymphoid tissue (BALT) which is located at the junctions between the primary bronchus and the caudal secondary bronchi. BALT nodules are absent in newly hatched birds, but gradually developed into the mature structures found from 6-8 weeks onwards. They are organized into distinct B and T cell areas, frequently comprise germinal centres and are covered by a characteristic follicle-associated epithelium. The interstitial tissue of the parabronchial walls harbours large numbers of tissue macrophages and lymphocytes which are scattered throughout tissue. A striking feature of the avian lung is the low number of macrophages on the respiratory surface under non-inflammatory conditions. Stimulation of the lung by live bacteria but not by a variety of bacterial products elicits a significant efflux of activated macrophages and, depending on the pathogen, of heterophils. In addition to the cellular components humoral defence mechanisms are found on the lung surface including secretory IgA. The compartmentalisation of the immune system in the avian lung into BALT and non BALT-regions should be taken into account in studies on the host-pathogen interaction since these structures may have distinct functional properties during an immune response.

Air Sacs↗

PubMed2006

Inter- and intramolecular epitope spreading in equine recurrent uveitis.

PURPOSE: To test the hypothesis that inter- and intramolecular spreading to S-antigen (S-Ag) and interphotoreceptor retinoid binding protein (IRBP)-derived epitopes occurs in a spontaneous model of recurrent uveitis in the horse. METHODS: The immune response of eight horses with equine recurrent uveitis (ERU) was compared with that of five control horses with healthy eyes. Lymphocytes derived from peripheral blood (PBLs) were tested every 8 weeks for their reactivity against S-Ag and various S-Ag and IRBP-derived peptides for 12 to 39 months (median, 22 months). During uveitic episodes, additional blood samples were analyzed. RESULTS: Intermolecular epitope spreading was detectable in all ERU cases during the study. Intramolecular spreading occurred in seven (of eight) horses with ERU. Fourteen relapses were analyzed during the observation period. Ten uveitic episodes were accompanied by neoreactivity to S-Ag or IRBP-derived peptides during the relapse. Shifts in the immune response profile were also detectable without any clinical signs of inflammation. Eye-healthy control horses were negative at all time points in the in vitro proliferation assays. CONCLUSIONS: Inter- and intramolecular spreading was detectable in a spontaneous model of recurrent uveitis. The shifts in immunoreactivity could account for the remitting-relapsing character of the disease.

Animals↗

PubMed2005

Characterization of duck leucocytes by monoclonal antibodies.

cDNAs encoding CD3epsilon, CD4 and the alpha-chain of CD8 of ducks were cloned. Monoclonal antibodies against Pekin duck CD4 and CD8alpha revealed that the antigens were expressed by the majority of thymocytes and by subpopulations of CD3+ cells in peripheral tissues. CD8alpha cell surface expression was also found on 90% of bursal cells. The B cell specificity of a newly developed mab to the immunoglobulin light-chain (L-chain) was confirmed by double labelling studies with the chicken B-cell cytokine BAFF. Using these tools and a mab reacting with the cytoplasmic domain of CD3epsilon, we demonstrated that the CD8alpha molecule is expressed to high levels in CD3-positive T cells and at lower levels in CD3-negative bursal and peripheral B cells. Mab 2-4, which recognizes the chicken CD28 molecule, was found to react with CD4-positive duck lymphocytes and with CD8-positive duck T cells but not with CD8-positive B cells. Mab K1, which recognizes a common antigen on chicken thrombocytes and monocytes/macrophages, was found to react with duck thrombocytes and macrophages. Thus, a range of mabs is now available which will allow to phenotype the major leucocyte populations in ducks, a surrogate infection model for hepatitis B virus.

Amino Acid Sequence↗

PubMed2004

The interferon system of non-mammalian vertebrates.

Genetic analysis in mice and other mammals showed that the interferon (IFN) system is important for resistance to viral and bacterial infections. IFN is thought to play a similar role in non-mammalian species, although knowledge is lagging behind. Molecular cloning revealed low but significant conservation of IFN genes in birds and fish. Whereas chickens and other birds have multiple genes for IFN-alpha and single genes for IFN-beta and IFN-gamma like most mammals, fish appear to have fewer IFN genes. Nonetheless, regulation of IFN-alpha and IFN-beta genes in response to viral and non-viral activators is well conserved in birds and fish, and similar sets of genes are induced in response to IFN in mammalian and non-mammalian vertebrates. IFN-like activities were also observed in reptiles and amphibians, but genes encoding these activities have not yet been cloned. Insights into the IFN system of non-mammalian species may lead to improved prophylactic and therapeutic approaches against virus infections in poultry and fish.

Amphibians↗

PubMed2004

Synthesis of IFN-beta by virus-infected chicken embryo cells demonstrated with specific antisera and a new bioassay.

Transcripts of interferon-alpha (IFN-alpha) and IFN-beta genes are present in virus-infected chicken cells, but because of a lack of appropriate assays and reagents, it was unclear if biologically active IFN-beta is secreted. We have established a nonviral bioassay for the sensitive detection of chicken IFN (ChIFN). This assay is based on a quail cell line that carries a luciferase gene that is controlled by the IFN-responsive chicken Mx promoter. Luciferase activity was strongly stimulated when the indicator cells were incubated with ChIFN-alpha, ChIFN-beta, or ChIFN-gamma but not with chicken interleukin-1beta (ChIL-1beta). Unlike the classic antiviral assay that preferentially detects ChIFN-alpha, the Mx-luciferase assay detected ChIFN-alpha and ChIFN-beta with similar sensitivity. With the help of this novel assay and with rabbit antisera specific for either IFN-alpha or IFN-beta, we analyzed the composition of IFN in supernatants of virus-infected chicken embryo cells. Virtually all IFN produced in response to Newcastle disease virus (NDV) was IFN-alpha. However, IFN produced in response to influenza A or vaccinia virus (VV) was a mixture of usually more than 80% IFN-alpha and up to 20% IFN-beta. Thus, IFN-alpha and IFN-beta both contribute to the cytokine activity in supernatants of virus-infected chicken cells. Furthermore, the infecting virus appears to determine the IFN subtype composition.

Animals↗

PubMed2004

Chicken BAFF--a highly conserved cytokine that mediates B cell survival.

Members of the tumor necrosis factor (TNF) family play key roles in the regulation of inflammation, immune responses and tissue homeostasis. Here we describe the identification of the chicken homologue of mammalian B cell activating factor of the TNF family (BAFF/BLyS). By searching a chicken EST database we identified two overlapping cDNA clones that code for the entire open reading frame of chicken BAFF (chBAFF), which contains a predicted transmembrane domain and a putative furin protease cleavage site like its mammalian counterparts. The amino acid identity between soluble chicken and human BAFF is 76%, considerably higher than for most other known cytokines. The chBAFF gene is most strongly expressed in the bursa of Fabricius. Soluble recombinant chBAFF produced by human 293T cells interacted with the mammalian cell-surface receptors TACI, BCMA and BAFF-R. It bound to chicken B cells, but not to other lymphocytes, and it promoted the survival of splenic chicken B cells in culture. Furthermore, bacterially expressed chBAFF induced the selective expansion of B cells in the spleen and cecal tonsils when administered to young chicks. Our results suggest that like its mammalian counterpart, chBAFF plays an important role in survival and/or proliferation of chicken B cells.

Amino Acid Sequence↗

PubMed2004

The uveitogenic potential of retinal S-antigen in horses.

PURPOSE: To investigate the uveitogenic potential of retinal S-antigen (S-Ag) in horses. METHODS: Horses were immunized subcutaneously with S-Ag or BSA as control antigen, emulsified in complete Freund's adjuvant. Simultaneously, Bordetella pertussis was given intravenously. Antigen specific T- and B-cell responses were analyzed in a 3-day interval. Disease development was judged clinically and histopathologically. Two identical booster immunizations were given every 4 weeks to test induction of recurrences. RESULTS: T- and B-cell responses specific for S-Ag were observed in all immunized horses but were absent in control animals. However, uveitis developed in only one of five animals. Reimmunization with S-Ag did not lead to a uveitic relapse in this horse. All other horses of the S-Ag- and BSA-treated groups neither showed any signs of uveitis, nor had inflammatory infiltrates of the inner eye. CONCLUSIONS: In contrast to interphotoreceptor retinoid-binding protein (IRBP), S-Ag is a weak autoantigen in horses. Even though S-Ag immunization leads to the activation of autoreactive T- and B-cells, infiltration of the inner eye and induction of uveitis are controlled in most horses.

Animals↗

PubMed2003

IL-18 stimulates the proliferation and IFN-gamma release of CD4+ T cells in the chicken: conservation of a Th1-like system in a nonmammalian species.

The phylogeny of Th1 and Th2 subsets has not been characterized mainly due to the limited information regarding cytokines in nonmammalian vertebrates. In this study, we characterize a Th1-like regulatory system focusing on the IL-18-regulated IFN-gamma secretion. Stimulation of splenocytes with chicken IL-18 induced high levels of IFN-gamma secretion. Depletion of either macrophages or CD4(+) T cells from the splenocyte cultures caused unresponsiveness to IL-18. In contrast, PBL were unresponsive to IL-18 in the presence or absence of macrophages, but IFN-gamma secretion was stimulated by suboptimal anti-TCR cross-linking combined with IL-18. Splenocytes from five different chicken lines responded equally well to the IL-18 treatment. LSL chicken splenocytes, however, responded only to IL-18 when stimulated either with optimal TCR cross-linking alone or suboptimal TCR cross-linking combined with IL-18. IL-18 not only induced IFN-gamma secretion, but also stimulated splenocyte proliferation. This IL-18-induced proliferation was compared with the effects observed with IL-2. Both cytokines activated the splenocytes as demonstrated by increased size and MHC class II Ag up-regulation in the case of IL-18. Phenotypic analyses following 6 days of culture revealed that IL-2 mainly affected the proliferation of CD8(+) cells, whereas IL-18 had an opposite effect and stimulated the proliferation of CD4(+) cells. Taken together, these results demonstrate the conservation of Th1-like proinflammatory responses in the chicken; they characterize IL-18 as a major growth factor of CD4(+) T cells and identify two distinct mechanisms of IL-18-induced IFN-gamma secretion.

Animals↗

PubMed2003

A sensitive bioassay for chicken interleukin-18 based on the inducible release of preformed interferon-gamma.

Conventional tests for measuring the biological activity of chicken interleukin (IL)-18 require primary chicken spleen cells. We now describe a sensitive bioassay that is based on interleukin-18-induced release of interferon (IFN)-gamma by a permanent chicken cell line. In B19-2D8 cells, cytoplasmically stored interferon-gamma is quickly secreted in response to interleukin-18 exposure.

Animals↗

PubMed2003

Truncated chicken interleukin-1beta with increased biologic activity.

Chicken interleukin-1beta (ChIL-1beta) is synthesized as a precursor molecule that unlike its mammalian counterpart, lacks a typical caspase-1 cleavage site. Therefore, it was unclear if proteolytic cleavage of ChIL-1beta can occur and if cleavage might modulate the biologic activity of this cytokine. Using an avian indicator cell line that carries an NF-kappaB-regulated luciferase reporter gene, we established a sensitive and highly specific bioassay for ChIL-1beta. Experiments with a rabbit antiserum indicated that the NF-kappaB-stimulating activity in supernatants of lipopolysaccharide (LPS)-treated chicken HD-11 macrophages is largely due to IL-1beta and that proteolytic processing of natural and recombinant ChIL-1beta is not very efficient. Functional analyses further revealed that cDNAs for either full-length or N-terminally truncated chicken ChIL-1beta yielded active cytokine. A truncated molecule that closely resembled putative mature ChIL-1beta exhibited more than 100-fold enhanced biologic activity after expression in mammalian cells, indicating that precursor cleavage is indeed of critical importance for maximal activity.

Animals↗

PubMed2003

Replication of modified vaccinia virus Ankara in primary chicken embryo fibroblasts requires expression of the interferon resistance gene E3L.

Highly attenuated modified vaccinia virus Ankara (MVA) serves as a candidate vaccine to immunize against infectious diseases and cancer. MVA was randomly obtained by serial growth in cultures of chicken embryo fibroblasts (CEF), resulting in the loss of substantial genomic information including many genes regulating virus-host interactions. The vaccinia virus interferon (IFN) resistance gene E3L is among the few conserved open reading frames encoding viral immune defense proteins. To investigate the relevance of E3L in the MVA life cycle, we generated the deletion mutant MVA-DeltaE3L. Surprisingly, we found that MVA-DeltaE3L had lost the ability to grow in CEF, which is the first finding of a vaccinia virus host range phenotype in this otherwise highly permissive cell culture. Reinsertion of E3L led to the generation of revertant virus MVA-E3rev and rescued productive replication in CEF. Nonproductive infection of CEF with MVA-DeltaE3L allowed viral DNA replication to occur but resulted in an abrupt inhibition of viral protein synthesis at late times. Under these nonpermissive conditions, CEF underwent apoptosis starting as early as 6 h after infection, as shown by DNA fragmentation, Hoechst staining, and caspase activation. Moreover, we detected high levels of active chicken alpha/beta IFN (IFN-alpha/beta) in supernatants of MVA-DeltaE3L-infected CEF, while moderate IFN quantities were found after MVA or MVA-E3rev infection and no IFN activity was present upon infection with wild-type vaccinia viruses. Interestingly, pretreatment of CEF with similar amounts of recombinant chicken IFN-alpha inhibited growth of vaccinia viruses, including MVA. We conclude that efficient propagation of MVA in CEF, the tissue culture system used for production of MVA-based vaccines, essentially requires conserved E3L gene function as an inhibitor of apoptosis and/or IFN induction.

Animals↗

PubMed2002

An interferon-gamma-binding protein of novel structure encoded by the fowlpox virus.

Poxviruses have evolved various strategies to counteract the host immune response, one of which is based on the expression of soluble cytokine receptors. Using various biological assays, we detected a chicken interferon-gamma (chIFN-gamma)-neutralizing activity in supernatants of fowlpox virus (FPV)-infected cells that could be destroyed by trypsin treatment. Secreted viral proteins were purified by affinity chromatography using matrix-immobilized chIFN-gamma, followed by two-dimensional gel electrophoresis. Matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) analysis indicated that the viral IFN-gamma-binding protein in question was encoded by the FPV gene 016. The chicken IFN-gamma binding and neutralizing activity of the recombinant FPV016 protein was confirmed using supernatants of cells infected with a recombinant vaccinia virus that lacked its own IFN-gamma-binding protein but instead expressed the FPV016 gene. The FPV016 gene product also neutralized the activity of duck and human IFN-gamma but failed to neutralize the activity of mouse and rat IFN-gamma. Unlike previously known cellular and poxviral IFN-gamma receptors, which all contain fibronectin type III domains, the IFN-gamma-binding protein of FPV contains an immunoglobulin domain. Remarkably, it exhibits no significant homology to any known viral or cellular protein. Because IFN-gamma receptors of birds have not yet been characterized at the molecular level, the possibility remains that FPV016 represents a hijacked chicken gene and that avian and mammalian IFN-gamma receptors have fundamentally different primary structures.

Amino Acid Sequence↗

PubMed2002

Uveitis in horses induced by interphotoreceptor retinoid-binding protein is similar to the spontaneous disease.

Equine recurrent uveitis (ERU) is an inflammatory eye disease with high similarity to uveitis in man. It is the only spontaneous animal model for uveitis and the most frequent eye disease in horses affecting up to 10% of the population. To further investigate the pathophysiology of ERU we now report the establishment of an inducible uveitis model in horses. An ERU-like disease was elicited in seven out of seven horses by injection of interphotoreceptor retinoid-binding protein (IRBP) in complete Freund's adjuvant. Control horses did not develop uveitis. The disease model is characterized by a highly reproducible disease course and recurrent episodes with an identical time course elicited in all horses by repeated IRBP injections. The histology revealed the formation of lymphoid follicle-like structures in the eyes and an intraocular infiltration dominated by CD3(+) lymphocytes, morphological patterns typical for the spontaneous disease. Antigen-specific T cell proliferation of PBL was monitored prior to clinical uveitis and during disease episodes. An initial T cell response to IRBP-derived peptides was followed by epitope spreading to S-antigen-derived peptides in response to subsequent immunizations. Thus, horse experimental uveitis represents a valuable disease model for comparative studies with the spontaneous disease and the investigation of immunomodulatory therapeutic approaches after onset of the disease.

Amino Acid Sequence↗

PubMed2002

Normal structure and age-related changes of the equine retina.

Investigations of the pathophysiology of ocular diseases require a detailed knowledge of the microanatomy of the eye. The available information is still inadequate for the equine retina despite the importance of eye diseases in equine medicine. Here we provide a comprehensive analysis of the histologic features of the horse eye as a reference for future studies. Thirty normal eyes of 15 healthy horses were examined immediately after slaughter. The retina of the horse differs considerably in the degree and quantity of neurons and glial elements as well as in vascular patterns compared to the retina of other domestic animals. Morphometric analysis revealed that the thickness of the retina varies between 80 microm at the ora serrata and 250 microm medial to the optic disc. Approximately 90% of the equine retina is comparatively thin (< 130 microm). This is a physiologic response to the distance that oxygen can diffuse in avascular retina. Ganglion cells form a single layer in all parts of the retina. The majority of ganglion cells are very large Nissl-positive cells. Small Nissl-negative ganglion cells are less abundant. A high ganglion cell density is found only in the central area. Vascularization is virtually absent from the retina with the exception of a narrow strip around the disc of the optic nerve, as revealed by lectin histochemistry. Light microscopy of the eyes of older horses repeatedly revealed cystoid degenerations in the retina adjacent to the pars plana of the ciliary body, as well as a destruction of the regular layering of the peripheral region of the retina.

Aging↗

PubMedDate not supplied

Thyroid sonography as an effective tool to discriminate between euthyroid sick and hypothyroid dogs.

The diagnosis of canine hypothyroidism and its differentiation from euthyroid sick syndrome still is a major diagnostic challenge. In this study, ultrasonography was shown to be an effective tool for the investigation of thyroid gland diseases. Healthy control dogs (n = 87), dogs with euthyroid sick syndrome (n = 26), thyroglobulin autoantibody-positive (TgAA-positive, n = 30) hypothyroid dogs, and TgAA-negative (n = 23) hypothyroid dogs were examined by thyroid ultrasonography. Maximal cross sectional area (MCSA), thyroid volume, and echogenicity were measured. Statistical analysis identified highly significant (P < .001) differences between euthyroid and hypothyroid dogs both in thyroid volume and in MCSA, whereas no significant differences in thyroid size were detected between healthy euthyroid dogs and dogs with euthyroid sick syndrome. In euthyroid and euthyroid sick dogs, parenchymal echotexture was homogeneous and hyperechoic, whereas relative thyroid echogenicity of both TgAA-positive and TgAA-negative hypothyroid dogs was significantly lower (P < .001). When using arbitrarily chosen cutoff values for relative thyroid volume, MCSA, and echogenicity, thyroid volume especially was found to have highly specific predictive value for canine hypothyroidism. In summary, the data reveal that thyroid sonography is an effective ancillary diagnostic tool to differentiate between canine hypothyroidism and euthyroid sick syndrome.

Animals↗