| 1. |
- Bax, Marieke, et al.
(författare)
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Dendritic cell maturation results in pronounced changes in glycan expression affecting recognition by siglecs and galectins
- 2007
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Ingår i: Journal of Immunology. - 1550-6606. ; 179:12, s. 8216-8224
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Tidskriftsartikel (refereegranskat)abstract
- Dendritic cells (DC) are the most potent APC in the organism. Immature dendritic cells (iDC) reside in the tissue where they capture pathogens whereas mature dendritic cells (mDC) are able to activate T cells in the lymph node. This dramatic functional change is mediated by an important genetic reprogramming. Glycosylation is the most common form of posttranslational modification of proteins and has been implicated in multiple aspects of the immune response. To investigate the involvement of glycosylation in the changes that occur during DC maturation, we have studied the differences in the glycan profile of iDC and mDC as well as their glycosylation machinery. For information relating to glycan biosynthesis, gene expression profiles of human monocyte-derived iDC and mDC were compared using a gene microarray and quantitative real-time PCR. This gene expression profiling showed a profound maturation-induced up-regulation of the glycosyltransferases involved in the expression of LacNAc, core 1 and sialylated structures and a down-regulation of genes involved in the synthesis of core 2 O-glycans. Glycosylation changes during DC maturation were corroborated by mass spectrometric analysis of N- and O-glycans and by flow cytometry using plant lectins and glycan-specific Abs. Interestingly, the binding of the LacNAc-specific lectins galectin-3 and -8 increased during maturation and up-regulation of sialic acid expression by mDC correlated with an increased binding of siglec-1, -2, and -7.
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| 2. |
- Zaccai, Nathan R., et al.
(författare)
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Crystallographic and in silico analysis of the sialoside-binding characteristics of the Siglec sialoadhesin
- 2007
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Ingår i: Journal of Molecular Biology. - : Elsevier BV. - 0022-2836 .- 1089-8638. ; 365:5, s. 1469-1479
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Tidskriftsartikel (refereegranskat)abstract
- The Siglec family of receptors mediates cell-surface interactions through recognition of sialylated glycoconjugates. Previously reported structures of the N-terminal domain of the Siglec sialoadhesin (SnD1) in complex with various sialic acid analogs revealed the structural template for sialic acid binding. To characterize further the carbohydrate-binding properties, we have determined the crystal structures of SnD1 in the absence of ligand, and in complex with 2-benzyl-Neu5NPro and 2-benzyl-Neu5NAc. These structures reveal that SnD1 undergoes very few structural changes on ligand binding and detail how two novel classes of sialic acid analogs bind, one of which unexpectedly can induce Siglec dimerization. In conjunction with in silico analysis, this set of structures informs us about the design of putative ligands with enhanced binding affinities and specificities to different Siglecs, and provides data with which to test the effectiveness of different computational drug design protocols.
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| 3. |
- Brook, Adam, et al.
(författare)
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Cell free hemoglobin in the fetoplacental circulation : A novel cause of fetal growth restriction?
- 2018
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Ingår i: FASEB Journal. - 0892-6638. ; 32:10, s. 5436-5446
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Tidskriftsartikel (refereegranskat)abstract
- Cell free hemoglobin impairs vascular function and blood flow in adult cardiovascular disease. In this study, we investigated the hypothesis that free fetal hemoglobin (fHbF) compromises vascular integrity and function in the fetoplacental circulation, contributing to the increased vascular resistance associated with fetal growth restriction (FGR). Women with normal and FGR pregnancies were recruited and their placentas collected freshly postpartum. FGRfetal capillaries showed evidence of erythrocyte vascular packing and extravasation. Fetal cord blood fHbF levels were higher in FGR than in normal pregnancies (P < 0.05) and the elevation of fHbF in relation to heme oxygenase-1 suggests a failure of expected catabolic compensation,which occurs in adults.During ex vivo placental perfusion, pathophysiological fHbF concentrations significantly increased fetal-side microcirculatory resistance (P<0.05). fHbF sequesteredNOinacute andchronic exposuremodels (P<0.001), andfHbF-primed placental endothelial cellsdevelopedaproinflammatoryphenotype,demonstratedby activationofNF-κBpathway, generation of IL-1α and TNF-α (both P < 0.05), uncontrolled angiogenesis, and disruption of endothelial cell flow alignment. Elevated fHbF contributes to increased fetoplacental vascular resistance and impaired endothelial protection.Thisunrecognizedmechanismfor fetal compromise offers a novel insight into FGRaswell as a potential explanation for associated poor fetal outcomes such as fetal demise and stillbirth.
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| 4. |
- Sancho Pelluz, Javier, et al.
(författare)
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Sialoadhesin Expression in Intact Degenerating Retinas and Following Transplantation.
- 2008
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Ingår i: Investigative Ophthalmology & Visual Science. - : Association for Research in Vision and Ophthalmology (ARVO). - 1552-5783. ; 49, s. 5602-5610
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Resident microglial cells normally do not express sialoadhesin (a sialic acid binding receptor), whereas recruited inflammatory macrophages have been shown to do so. The expression of sialoadhesin was examined here in the course of photoreceptor cell degeneration and following transplantation. Methods: Sialoadhesin expression was analyzed in retinas of rd1 and rds mice. For transplantation studies, neonatal (P2) retinal cells derived from GFP mice were injected intraocularly in adult rd1 mice and controls. Antibodies recognizing different sialoadhesin epitopes, CD11b, and MHC-II were used to identify activated microglial cells in intact retinas and 21 days post-transplantation. Results: In rd1 mice, a few CD11b-positive cells were observed in the outer nuclear layer in the central retina at postnatal day (P) 11 and in increasing numbers between P12 21. In rds mice, CD11b-expressing cells were found from P16 and onwards. No sialoadhesin expressing cells were observed within the rd1 or rds mouse retinas at any of the ages examined (up to P150). Specific staining was only observed in cells found in the vitreal margin of the retina and in surrounding tissues (sclera, cornea, ciliary body, choroid). Following transplantation to normal and rd1 mice, a variable number of sialoadhesin-positive cells were detected within the grafts, in the graft-host interface, and in the subretinal space. Conclusions: The significant activation of microglia/macrophages observed in the various stages of degeneration in rd1 and rds mouse retinas is not accompanied by sialoadhesin expression. However, sialoadhesin-expressing cells are observed following transplantation. The occurrence of such cells could be of significance for the integration and long term survival of retinal grafts, as expression of sialoadhesin could facilitate other phagocytic receptors.
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| 5. |
- Wu, Chuan, et al.
(författare)
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Sialoadhesin-Positive Macrophages Bind Regulatory T Cells, Negatively Controlling Their Expansion and Autoimmune Disease Progression
- 2009
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Ingår i: Journal of Immunology. - : The American Association of Immunologists. - 1550-6606 .- 0022-1767. ; 182:10, s. 6508-6516
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Tidskriftsartikel (refereegranskat)abstract
- An important regulatory suppressive function in autoimmune and other inflammatory processes has been ascribed to CD4(+) Foxp3(+) regulatory T cells (Tregs), which requires direct cell-cell communication between Tregs, effector T cells, and APCs. However, the molecular basis for these interactions has not yet been clarified. We show here that sialoadhesin (Sn), the prototype of the siglec family of sialic acid-binding transmembrane proteins, expressed by resident and activated tissue-infiltrating macrophages, directly binds to Tregs, negatively regulating their expansion in an animal model of multiple sclerosis (MS), experimental autoimmune encephalomyelitis (EAE). In this model, macrophages infiltrate the CNS exhibiting tissue-destructing and demyelinating activity, leading to MS-like symptoms. We show here that severity of EAE symptoms is reduced in Sn knockout (KO) mice compared with wild-type littermates due to an up-regulation of CD4(+)Foxp3(+) Treg lymphocytes. Through the use of a Sn fusion protein, Tregs were shown to express substantial amounts of Sri ligand on their cell surface, and direct interaction of Sn+ macrophages with Tregs specifically inhibited Treg but not effector T lymphocyte proliferation. Conversely, blocking of Sn on macrophages by Sn-specific Abs resulted in elevated proliferation of Tregs. Data indicate that Sn+ macrophages regulate Treg homeostasis which subsequently influences EAE progression. We propose a new direct cell-cell interaction-based mechanism regulating the expansion of the Tregs during the immune response, representing a "dialogue" between Sn+ macrophages and Sn-accessible sialic acid residues on Treg lymphocytes. The Journal of Immunology, 2009, 182: 6508-6516.
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| 6. |
- Yrlid, Ulf, 1971, et al.
(författare)
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Plasmacytoid dendritic cells do not migrate in intestinal or hepatic lymph.
- 2006
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Ingår i: Journal of immunology (Baltimore, Md. : 1950). - 0022-1767. ; 177:9, s. 6115-21
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Tidskriftsartikel (refereegranskat)abstract
- Plasmacytoid dendritic cells (pDCs) recognize pathogen-associated molecules, particularly viral, and represent an important mechanism in innate defense. They may however, also have roles in steady-state tolerogenic responses at mucosal sites. pDCs can be isolated from blood, mucosa, and lymph nodes (LNs). Although pDCs can express peripherally derived Ags in LNs and at mucosal sites, it is not clear whether pDCs actually migrate from the periphery in lymph or whether LN pDCs acquire Ags by other mechanisms. To determine whether pDCs migrate in lymph, intestine or liver-draining LNs were removed and thoracic duct leukocytes (TDLs) were collected. TDLs expressing MHC-II and CD45R, but not TCRalphabeta or CD45RA, were then analyzed. These enriched TDLs neither transcribe type I IFNs nor secrete inflammatory cytokines in response to viral stimuli in vitro or after a TLR7/8 stimulus in vivo. In addition, these TDLs do not express CD5, CD90, CD200, or Siglec-H, but do express Ig, and therefore represent B cells, despite their lack of CD45RA expression. Intestinal and hepatic lymph are hence devoid of bona fide pDCs under both steady-state conditions and after TLR7/8 stimulation. This shows that any role for pDCs in Ag-specific T cell activation or tolerance must differ from the roles of classical dendritic cells, because it cannot result from peripheral Ag capture, followed by migration of pDCs via lymph to the LN.
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