| 1. |
- Lucas, Beth, et al.
(författare)
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CCRL1/ACKR4 is expressed in key thymic microenvironments but is dispensable for T lymphopoiesis at steady state in adult mice
- 2015
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Ingår i: European Journal of Immunology. - : Wiley. - 1521-4141 .- 0014-2980. ; 45:2, s. 574-583
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Tidskriftsartikel (refereegranskat)abstract
- Thymus colonisation and thymocyte positioning are regulated by interactions between CCR7 and CCR9, and their respective ligands, CCL19/CCL21 and CCL25. The ligands of CCR7 and CCR9 also interact with the atypical receptor CCRL1 (also known as ACKR4), which is expressed in the thymus and has recently been reported to play an important role in normal alpha beta T-cell development. Here, we show that CCRL1 is expressed within the thymic cortex, predominantly by MHC-II(low)CD40(-) cortical thymic epithelial cells and at the subcapsular zone by a population of podoplanin(+) thymic epithelial cells in mice. Interestingly, CCRL1 is also expressed by stromal cells which surround the pericytes of vessels at the corticomedullary junction, the site for progenitor cell entry and mature thymocyte egress from the thymus. We show that CCRL1 suppresses thymocyte progenitor entry into the thymus, however, the thymus size and cellularity are the same in adult WT and CCRL1(-/-) mice. Moreover, CCRL1(-/-) mice have no major perturbations in T-cell populations at different stages of thymic differentiation and development, and have a similar rate of thymocyte migration into the blood. Collectively, our findings argue against a major role for CCRL1 in normal thymus development and function.
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| 2. |
- Massena, Sara, et al.
(författare)
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Chemokine transport across the vessel wall and presentation to circulation leukocytes are regulated by vascular permeability, DARC and PAD released during inflammation
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Annan publikation (populärvet., debatt m.m.)abstract
- Increased vascular permeability and consequent leakage of plasma and macromolecules through endothelial cell junctions is a hallmark of inflammation. The physiological importance of this event for leukocyte recruitment has been controversial, but it might have a role in chemokine transport into blood vessels and consequently for the recruitment of circulating leukocytes. Elevated amounts of peptidyl arginine deiminases (PAD) and of their citrullinated products associate with autoimmune disorders, chronic inflammation and cancer. The role of citrullination in the inflamed microenvironment is debated, but it might be an innate mechanism for infiltrating leukocytes to resolve inflammation. In this study we investigated if increased vascular permeability facilitated the influx of chemokines from tissue into post-capillary venules, thereby affecting leukocyte recruitment. Vascular permeability and chemokine influx into post-capillary venules were simultaneously monitored by real-time in vivo confocal microscopy of the mouse cremaster muscle. We found that increased venular permeability induced by histamine, correlated with accelerated influx of the fluorescently labeled chemokine CXC ligand 2 (CXCL2/MIP-2) into post-capillary venules, which accumulated predominantly at endothelial cell junctions. Consequently, neutrophil adhesion was accelerated leading to increased neutrophil extravasation. In situ inhibition of caveolae-mediated transcytosis by filipin had no significant effect on chemokine influx to post-capillary venules, indicating that chemokine traffic across the venular wall is independent of caveolar transport. Nevertheless, neutrophil recruitment was prevented in filipin-treated mice as transmigrating neutrophils were trapped on endothelial cell domes and failed to finalize transmigration. Furthermore, we used this real-time in vivo model for studying the role of the atypical chemokine receptor 1 (DARC/ACKR1) in chemokine transport and availability. We show that the absence of DARC/ACKR1 (ACKR1-/- mice) does not impair chemokine transport. Instead it leads to increased seric levels of chemokine and increased intravascular chemokine sequestration. As a result, high numbers of firmly adherent neutrophils were found in post-capillary venules. Intraluminal neutrophil crawling was though abrogated and neutrophil transmigration prevented. Finally, we studied the role of chemokine citrullination by leukocyte-derived PAD in the inflamed tissue. The transport of citrullinated CXC ligand 8 (CXCL8/IL-8) across the venular wall, its immobilization on the luminal endothelium, and subsequent leukocyte recruitment, were monitored by real time imaging. Chemokine citrullination inhibited its transport from the inflamed tissue into blood vessels, impeding their immobilization on the luminal endothelium. Reduced intravascular chemokine bioavailability dampened leukocyte recruitment. Altogether these findings demonstrate that changes in vascular permeability regulate inflammation by affecting abluminal-to-luminal chemokine transport and thereby leukocyte recruitment to tissue. Furthermore, DARC/ACKR1 plays an important role in neutrophil recruitment by controlling intravascular chemokine availability and by shaping the intravascular chemokine gradient necessary for efficient neutrophil recruitment. Finally, citrullination of chemokines by PAD in the inflamed tissue inhibits chemokine transport into blood vessels and luminal presentation to circulating leukocytes, which dampens leukocyte recruitment
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| 3. |
- Ulvmar, Maria H, et al.
(författare)
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The atypical chemokine receptor CCRL1 shapes functional CCL21 gradients in lymph nodes.
- 2014
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Ingår i: Nature Immunology. - : Springer Science and Business Media LLC. - 1529-2908 .- 1529-2916. ; 15:7
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Tidskriftsartikel (refereegranskat)abstract
- Afferent lymph-borne dendritic cells essentially rely on the chemokine receptor CCR7 for their transition from the subcapsular lymph node sinus into the parenchyma, a migratory step driven by putative gradients of CCR7 ligands. We found that lymph node fringes indeed contained physiological gradients of the chemokine CCL21, which depended on the expression of CCRL1, the atypical receptor for the CCR7 ligands CCL19 and CCL21. Lymphatic endothelial cells lining the ceiling of the subcapsular sinus, but not those lining the floor, expressed CCRL1, which scavenged chemokines from the sinus lumen. This created chemokine gradients across the sinus floor and enabled the emigration of dendritic cells. In vitro live imaging revealed that spatially confined expression of CCRL1 was necessary and sufficient for the creation of functional chemokine gradients.
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