Dermal Lymphatic Vessels Research Articles

Targeted overexpression of Angptl6/angiopoietin‐related growth factor in the skin promotes angiogenesis and lymphatic vessel enlargement in response to ultraviolet B

Angiogenesis is required for physiological tissue repair processes, such as cutaneous wound healing. However, recent studies indicate that endogenous angiogenic factors may enhance photo-induced skin alterations in response to experimental ultraviolet (UV)-B exposure. Angiopoietin-related growth factor (AGF), also known as angiopoietin-like protein 6 (Angptl6), is known to promote new blood vessel formation and vascular hyperpermeability. Importantly, epidermal overexpression of Angptl6/AGF in mice promotes wound healing in the skin. However, it remains unclear whether overexpression of Angptl6/AGF facilitates tissue repair processes in response to UV-B irradiation. To test this hypothesis, we subjected Angptl6/AGF transgenic mice to acute or chronic UV-B exposure. Surprisingly, transgenic mice showed enhanced photosensitivity to subthreshold doses of UV-B that did not induce skin alterations in wild-type littermates. Marked enlargement of blood vessels was observed after a single exposure to UV-B in Angptl6/AGF transgenic mice, although no epidermal changes were observed. Chronic UV-B exposure over 14 weeks promoted cutaneous skin damage in Angptl6/AGF transgenic mice, whereas wild-type mice showed little or no macroscopic skin alteration. In addition to pronounced angiogenesis and epidermal hyperplasia, marked enlargement of dermal lymphatic vessels was observed in UV-B-exposed Angptl6/AGF transgenic mice. Electron microscopy analysis further revealed that the number and size of collagen bundles in the dermis was markedly reduced after chronic UV-B exposure in Angptl6/AGF transgenic mice. Taken together, these results indicate that ectopic expression of Angptl6/AGF in mice likely promotes UV-B-induced skin alterations, and that angiogenesis could be a therapeutic target in prevention of skin photo-aging.

Erysipelas after breast cancer treatment

Erysipelas is a distinct type of superficial cutaneous cellulitis with marked dermal lymphatic vessel involvement caused by group A beta hemolytic streptococcus (very uncommonly group C or C streptococcus) and rarely caused by S. aureus. Lymphedema, venous stasis, web intertrigo, and obesity are risk factors in the adult patient.1 Erysipelas of the upper extremity following breast cancer treatment was vaguely described as a complication in a German-language journal2 and as a case report in a Dutch-language journal.

Role of COX-2 in lymphangiogenesis and restoration of lymphatic flow in secondary lymphedema

The pathophysiology of secondary lymphedema remains poorly understood. To clarify the roles of cyclooxygenase (COX)-2 in enhancement of lymphangiogenesis during secondary lymphedema, we tested a mouse tail model and evaluated the recurrence of lymph flow. To induce lymphedema, a circumferential incision was made in the tail of anesthetized mice to sever the dermal lymphatic vessels. The maximum diameters of the tails were measured weekly. We found that the diameters of the tails around the wounds were markedly increased after surgery, and reached maximum size 2 weeks after wounding in mice without a COX-2 inhibitor, celecoxib (Celecoxib–). Expression of COX-2 in wound granulation tissues was markedly increased 1 week after surgery compared with unwounded naive control mice. In Celecoxib–, recurrence of lymphatic flow in the wound granulation tissues was detected 3 weeks after surgical treatment. In contrast, lymphatic flow was markedly suppressed in mice treated with celecoxib (Celecoxib+). Newly formed lymphatic structures were identified in the granulation tissues formed at wounded lesions in Celecoxib–, whereas those were markedly suppressed in Celecoxib+. Interstitial tissue pressures in the distal areas of the tail wounds were markedly increased in Celecoxib+ with reduced expression of vascular endothelial cell growth factor (VEGF)-C. F4/80-positive cells were accumulated to the wound granulation tissues in Celecoxib–, and the accumulation of these cells was suppressed in Celecoxib+. Prostaglandin E2 (PGE2) upregulated the expressions of VEGF-A and VEGF-C in cultured macrophages, but not human lymphatic microvascular endothelial cells. The present study therefore suggests that lymphangiogenesis, together with recurrence of lymph flow after surgical induction of lymphedema, is upregulated by COX-2 possibly via generation of PGs.

Peripheral lymphangiogenesis in mice depends on ectodermal connexin-26 (Gjb2)

In order to study the specific function of connexin-26 (Cx26, also known as gap junction beta-2 protein; Gjb2), we generated knockin mice that expressed either a floxed lacZ reporter or, after Cre-mediated deletion, connexin-32 (Cx32)-coding DNA, both driven by the endogenous Cx26 promoter. Heterozygous Cx26knock-inCx32 (Cx26KICx32) embryos developed normally until embryonic day 14.5 but died before birth with severe lymphedemas. Although the jugular lymph sacs were normally developed, these embryos had a strongly reduced dermal lymphatic capillary network. By analyses of β-galactosidase reporter protein expression and lymphatic or blood endothelial-specific marker proteins, we demonstrated that Cx26 expression is temporally closely linked to lymphangiogenesis. No obvious phenotypic abnormalities were observed in Cx26KICx32 mice when Cre-mediated recombination was directed to mesenchyme or blood endothelium using the Prx1-Cre or Tie2-Cre mouse strains, respectively. By contrast, keratin-5-Cre-mediated replacement of Cx26 with Cx32 or deletion of both Cx26 alleles revealed severe lymphedemas similar to the general Cx26KICx32 phenotype. Thus, conditional ablation of Cx26 (loss of function) in ectoderm leads to partial disruption of lymphatic capillaries and embryonic death. We conclude that appropriate development of dermal lymphatic vessels in mice is dependent on the expression of Cx26 in the ectoderm.

Peripheral lymphangiogenesis in mice depends on ectodermal connexin-26 (Gjb2)

In order to study the specific function of connexin-26 (Cx26, also known as gap junction beta-2 protein; Gjb2), we generated knockin mice that expressed either a floxed lacZ reporter or, after Cre-mediated deletion, connexin-32 (Cx32)-coding DNA, both driven by the endogenous Cx26 promoter. Heterozygous Cx26knock-inCx32 (Cx26KICx32) embryos developed normally until embryonic day 14.5 but died before birth with severe lymphedemas. Although the jugular lymph sacs were normally developed, these embryos had a strongly reduced dermal lymphatic capillary network. By analyses of β-galactosidase reporter protein expression and lymphatic or blood endothelial-specific marker proteins, we demonstrated that Cx26 expression is temporally closely linked to lymphangiogenesis. No obvious phenotypic abnormalities were observed in Cx26KICx32 mice when Cre-mediated recombination was directed to mesenchyme or blood endothelium using the Prx1-Cre or Tie2-Cre mouse strains, respectively. By contrast, keratin-5-Cre-mediated replacement of Cx26 with Cx32 or deletion of both Cx26 alleles revealed severe lymphedemas similar to the general Cx26KICx32 phenotype. Thus, conditional ablation of Cx26 (loss of function) in ectoderm leads to partial disruption of lymphatic capillaries and embryonic death. We conclude that appropriate development of dermal lymphatic vessels in mice is dependent on the expression of Cx26 in the ectoderm.

Histopathologic analysis of dermal lymphatic alterations in chronic venous insufficiency ulcers using D2-40

Chronic venous insufficiency (CVI) ulcers represent a major medical problem worldwide. Current theories concerning the pathogenesis of CVI ulcers focus on abnormalities in the blood vascular system. Other abnormalities, such as chronic leg edema, may also play pathogenic roles in CVI ulcer development and further understanding of such alterations may lead to better treatments. To gain insight into lymphatic abnormalities occurring in CVI, we compared dermal lymphatics in histologic sections from CVI ulcers and normal controls. We compared global and architectural features of dermal lymphatics in D2-40-stained histologic sections from CVI ulcer tissue and from normal controls. D2-40 recognizes podoplanin, a transmembrane glycoprotein that is constitutively expressed in lymphatic endothelial cells, allowing us to distinguish dermal blood vessels from lymphatic vessels. Our analyses reveal that CVI ulcer specimens have more dermal lymphatic vessels per unit area than controls (5.71 vs 4.08 per mm(2), respectively; P = .0281); a higher percentage of lymphatic vessels with collapsed lumina compared with controls (30.5% vs 8.1%, respectively; P < .0001); and a higher percentage of competent lymphatic vessels displaying open inter-endothelial junctions compared with controls (5.7% vs 2.9%, respectively; P < .0369). Our study is limited by its retrospective nature and relatively small sample size. Lymphatic vessels in CVI ulcer specimens display global and architectural differences compared with lymphatic vessels in control specimens. These findings further implicate lymphatic dysfunction in the pathogenesis of CVI ulcers and allow for the formulation of a hypothesis concerning lymphatic changes that may be tested in future studies.

Macrophages define dermal lymphatic vessel calibre during development by regulating lymphatic endothelial cell proliferation

Macrophages define dermal lymphatic vessel calibre during development by regulating lymphatic endothelial cell proliferation

Progressive Loss of Lymphatic Vessels in Skin of Patients with Systemic Sclerosis

Systemic sclerosis (SSc) is a connective tissue disorder characterized by microvascular and fibrotic changes in the skin and internal organs. The role of blood vessel dysfunction in the pathogenesis of SSc has been extensively investigated, but few studies have addressed the involvement of the lymphatic vascular system. Our aim was to evaluate dermal lymphatic vessels in patients with SSc according to different phases of skin involvement. Skin biopsies were obtained from the forearm of 25 SSc patients (10 early/15 late-stage disease) and 13 healthy controls. Skin sections were immunostained for podoplanin (D2-40), which is selectively expressed in lymphatic endothelial cells, and examined by confocal laser scanning microscopy. Lymphatic vessels were counted in the papillary and reticular dermis. Data were analyzed using Student's t test. The number of lymphatic vessels was significantly reduced in the papillary and reticular dermis of SSc patients compared with controls. In early SSc, lymphatic vessel counts were not different from controls in the papillary dermis, and showed a trend toward a reduction in the reticular dermis. In late SSc, a significant reduction in lymphatic vessels compared with controls was found in both the papillary and reticular dermis. The number of lymphatic vessels in the papillary dermis of late SSc was significantly lower than in early SSc. In SSc, lymphatic microangiopathy is linked to the progression of skin involvement. The progressive disappearance of lymphatic vessels may have a critical pathogenetic role in the progression of SSc from an early edematous phase to overt fibrosis.

Macrophages define dermal lymphatic vessel calibre during development by regulating lymphatic endothelial cell proliferation.

Macrophages have been suggested to stimulate neo-lymphangiogenesis in settings of inflammation via two potential mechanisms: (1) acting as a source of lymphatic endothelial progenitor cells via the ability to transdifferentiate into lymphatic endothelial cells and be incorporated into growing lymphatic vessels; and (2) providing a crucial source of pro-lymphangiogenic growth factors and proteases. We set out to establish whether cells of the myeloid lineage are important for development of the lymphatic vasculature through either of these mechanisms. Here, we provide lineage tracing evidence to demonstrate that lymphatic endothelial cells arise independently of the myeloid lineage during both embryogenesis and tumour-stimulated lymphangiogenesis in the mouse, thus excluding macrophages as a source of lymphatic endothelial progenitor cells in these settings. In addition, we demonstrate that the dermal lymphatic vasculature of PU.1–/– and Csf1r–/– macrophage-deficient mouse embryos is hyperplastic owing to elevated lymphatic endothelial cell proliferation, suggesting that cells of the myeloid lineage provide signals that act to restrain lymphatic vessel calibre in the skin during development. In contrast to what has been demonstrated in settings of inflammation, macrophages do not comprise the principal source of pro-lymphangiogenic growth factors, including VEGFC and VEGFD, in the embryonic dermal microenvironment, illustrating that the sources of patterning and proliferative signals driving embryonic and disease-stimulated lymphangiogenesis are likely to be distinct.

Macrophages define dermal lymphatic vessel calibre during development by regulating lymphatic endothelial cell proliferation

Macrophages have been suggested to stimulate neo-lymphangiogenesis in settings of inflammation via two potential mechanisms: (1) acting as a source of lymphatic endothelial progenitor cells via the ability to transdifferentiate into lymphatic endothelial cells and be incorporated into growing lymphatic vessels; and (2) providing a crucial source of pro-lymphangiogenic growth factors and proteases. We set out to establish whether cells of the myeloid lineage are important for development of the lymphatic vasculature through either of these mechanisms. Here, we provide lineage tracing evidence to demonstrate that lymphatic endothelial cells arise independently of the myeloid lineage during both embryogenesis and tumour-stimulated lymphangiogenesis in the mouse, thus excluding macrophages as a source of lymphatic endothelial progenitor cells in these settings. In addition, we demonstrate that the dermal lymphatic vasculature of PU.1(-/-) and Csf1r(-/-) macrophage-deficient mouse embryos is hyperplastic owing to elevated lymphatic endothelial cell proliferation, suggesting that cells of the myeloid lineage provide signals that act to restrain lymphatic vessel calibre in the skin during development. In contrast to what has been demonstrated in settings of inflammation, macrophages do not comprise the principal source of pro-lymphangiogenic growth factors, including VEGFC and VEGFD, in the embryonic dermal microenvironment, illustrating that the sources of patterning and proliferative signals driving embryonic and disease-stimulated lymphangiogenesis are likely to be distinct.

Radiation therapy causes loss of dermal lymphatic vessels and interferes with lymphatic function by TGF-beta1-mediated tissue fibrosis.

Although radiation therapy is a major risk factor for the development of lymphedema following lymphadenectomy, the mechanisms responsible for this effect remain unknown. The purpose of this study was therefore to determine the effects of radiation on lymphatic endothelial cells (LECs) and lymphatic function. The tails of wild-type or acid sphingomyelinase (ASM)-deficient mice were treated with 0, 15, or 30 Gy of radiation and then analyzed for LEC apoptosis and lymphatic function at various time points. To analyze the effects of radiation fibrosis on lymphatic function, we determined the effects of transforming growth factor (TGF)-beta1 blockade after radiation in vivo. Finally, we determined the effects of radiation and exogenous TGF-beta1 on LECs in vitro. Radiation caused mild edema that resolved after 12-24 wk. Interestingly, despite resolution of tail edema, irradiated animals displayed persistent lymphatic dysfunction. Radiation caused loss of capillary lymphatics and was associated with a dose-dependent increase in LEC apoptosis. ASM-/- mice had significantly less LEC apoptosis; however, this finding did not translate to improved lymphatic function at later time points. Short-term blockade of TGF-beta1 function after radiation markedly decreased tissue fibrosis and significantly improved lymphatic function but did not alter LEC apoptosis. Radiation therapy decreases lymphatic reserve by causing depletion of lymphatic vessels and LECs as well as promoting soft tissue fibrosis. Short-term inhibition of TGF-beta1 activity following radiation improves lymphatic function and is associated with decreased soft tissue fibrosis. ASM deficiency confers LEC protection from radiation-induced apoptosis but does not prevent lymphatic dysfunction.

Systemic anti-VEGF treatment strongly reduces skin inflammation in a mouse model of psoriasis

Although(,) vascular remodeling is a hallmark of many chronic inflammatory disorders such as rheumatoid arthritis, inflammatory bowel disease, and psoriasis, anti-vascular strategies to treat these conditions have received little attention to date. We investigated the anti-inflammatory activity of systemic blockade of VEGF-A by the inhibitory monoclonal antibody G6-31, employing a therapeutic trial in a mouse model of psoriasis. Simultaneous deletion of JunB and c-Jun (DKO*) in the epidermis of adult mice leads to a psoriasis-like phenotype with hyper- and parakeratosis and increased subepidermal vascularization. Moreover, an inflammatory infiltrate and elevated levels of cytokines/chemokines including TNFalpha, IL-1alpha/beta, IL-6, and the innate immune mediators IL-22, IL-23, IL-23R, and IL-12p40 are detected. Here we show that anti-VEGF antibody treatment of mice already displaying disease symptoms resulted in an overall improvement of the psoriatic lesions leading to a reduction in the number of blood vessels and a significant decrease in the size of dermal blood and lymphatic vessels. Importantly, anti-VEGF-treated mice showed a pronounced reduction of inflammatory cells within the dermis and a normalization of epidermal differentiation. These results demonstrate that systemic blockade of VEGF by an inhibitory antibody might be used to treat patients who have inflammatory skin disorders such as psoriasis.

Huffmanela sp. (Nematoda: Trichosomoididae) muscular parasite from Trisopterus luscus captured off the Portuguese coast

Four samples of Trisopterus luscus exhibiting unusual black spots on their musculature were obtained from catches made on different days and were rejected as unsuitable for consumption. Bipolar eggs somewhat resembling those of the nematode genus Huffmanela (Nematoda: Trichosomoididae) were identified as the cause of these black spots. Microscopic analysis revealed the presence of dark-shelled trichinelloid embryonated eggs dispersed throughout the muscle tissue, 73 to 94 x 40 to 59 microm in size, with large polar plugs 14 to 22 microm wide. However, the morphology and distribution of the observed eggs were not compatible with any previously described Huffmanela species. Intracellular nematodes were also observed in muscle cells. In 2 samples, sectioned nematode specimens were observed in other locations as well: the lymphatic vessel of intestine submucosa and the dermal lymphatic vessel. This could be due to nematode migration inside the infected fish. The presumed identification of Huffmanela sp. in a new host (Trisopterus luscus), and in a new location (Atlantic Ocean) supports the belief that these parasites could be widely distributed, particularly in marine fishes. In view of these factors, together with the observed egg morphology, it is possible that these specimens represent a new, unidentified Huffmanela species.

Classification of cutaneous intravascular breast cancer metastases based on immunolabeling for blood and lymph vessels

Intravascular breast cancer metastases to the skin can have several clinically distinct manifestations. Carcinoma telangiectoides, which presents as an erythematous patch with prominent telangiectasias or lymphangioma circumscriptum-like lesions, is a rare manifestation of cutaneous metastatic breast cancer and has been proposed to spread via dermal blood vessels. Carcinoma erysipelatoides, which presents as an erysipelas-like patch or plaque, has been proposed to spread via lymphatics. Clinical variants with nodular lesions that show tumor cells within vessels and in the extravascular space are seen more commonly. It has not been demonstrated conclusively whether dermal blood vessels or whether dermal lymph vessels are principally involved in these clinically distinct forms of cutaneous breast cancer metastases. We sought to determine if carcinoma telangiectoides affects predominantly dermal blood vessels and if carcinoma erysipelatoides affects predominantly dermal lymph vessels. Serial sections of biopsy specimens from patients with a characteristic clinical presentation of carcinoma telangiectoides and carcinoma erysipelatoides were labeled for cytokeratin to identify malignant cells. Subsequently, these sections were labeled for CD31 (a marker for blood and lymph vessels) and podoplanin (a marker for lymph vessels, but not for blood vessels), to differentiate blood vessels from lymph vessels in these sections. Sections from carcinoma telangiectoides showed malignant tumor cells strictly within dermal blood vessels, but not in lymph vessels. In contrast, sections from carcinoma erysipelatoides showed malignant tumor cells strictly in dermal lymphatics. We used typical clinical cases to demonstrate the distinct involvement of blood and lymph vessels in these variants of cutaneous metastatic breast cancer. A larger case series is needed to confirm these findings. Immunolabeling for CD31 and podoplanin of cutaneous lesions of metastatic breast cancer confirms the spread of tumor cells predominantly via lymphatics in carcinoma erysipelatoides and predominantly via blood vessels in carcinoma telangiectoides.

The lymph vessel network in mouse skin visualised with antibodies against the hyaluronan receptor LYVE-1

Langerhans cells and dermal dendritic cells migrate to the draining lymph nodes through dermal lymphatic vessels. They do so in the steady-state and under inflammatory conditions. Peripheral T cell tolerance or T cell priming, respectively, are the consequences of migration. The nature of dendritic cell-containing vessels was mostly defined by electron microscopy or by their lack of blood endothelial markers. Selective markers for murine lymph endothelium were hitherto rare or not available. Here, we utilised recently developed antibodies against the murine hyaluronan receptor, LYVE-1, to study the lymph vessel network in mouse skin in more detail. In hairless skin from the ears, lymph vessels were spread out in a horizontal plane. They formed anastomoses, and they possessed frequent blind endings that were occasionally open. Lymph vessels were wider than blood vessels, which were identified by their strong CD31 expression. In body wall skin LYVE-1 reactive vessels did not extend laterally but they dived straight down into the deeper dermis. There, they are connected to each other and formed a network similar to ear skin. The number and width of lymph vessels did not grossly change upon inflammatory stimuli such as skin explant culture or tape stripping. There were also no marked changes in caliber in response to the TLR 7/8 ligand Imiquimod. Double-labelling experiments of cultured skin showed that most of the strongly cell surface MHC II-expressing (i.e. activated) dendritic cells were confined to the lymph vessels. Langerin/CD207 + cells within this population appeared later than dermal dendritic cells, i.e. langerin-negative cells. Comparable results were obtained after stimulating the skin in vivo with the TLR 7/8 ligand Imiquimod or by tape stripping. In untreated skin (i.e. steady state) a few MHC II + and Langerin/CD207 + cells, presumably migrating skin dendritic cells including epidermal Langerhans cells, were consistently observed within the lymph vessels. The novel antibody reagents may serve as important tools to further study the dendritic cell traffic in the skin under physiological conditions as well as in conditions of adoptive dendritic cell transfer in immunotherapy.

Persistent lymphoedema in Morbihan disease: formation of perilymphatic epithelioid cell granulomas as a possible pathogenesis

Morbihan disease is a rare complication of rosacea, characterized by persistent lymphoedema on the upper half of the face, occurring during the chronic clinical course of rosacea. This refractory condition has been also designated as 'rosacea lymphoedema' and 'solid persistent facial oedema of rosacea'. We report a patient with Morbihan disease showing persistent lymphoedema on the upper half of the face accompanied by unique histological findings of striking dermal dilated lymphatics and damage of the lymphatics at the site of the adjacent epithelioid cell granulomas, with histiocytes bulging into the lymphatic lumen. The marked epithelioid cell granulomas forming around dermal lymphatic vessels with subsequent lymphatic damage and luminal obstruction by histiocytic infiltration may account for the development of lymphoedema in this patient.

Defective remodeling and maturation of the lymphatic vasculature in Angiopoietin-2 deficient mice

Molecular mechanisms regulating the remodeling of the lymphatic vasculature from an immature plexus of vessels to a hierarchal network of initial and collecting lymphatics are not well understood. One gene thought to be important for this process is Angiopoietin-2 (Ang-2). Ang2−/− mice have previously been reported to exhibit an abnormal lymphatic phenotype but the precise nature of the lymphatic defects and the underlying mechanisms have yet to be defined. Here we demonstrate by whole-mount immunofluorescence staining of ear skin and mesentery that lymphatic vessels in Ang2−/− mice fail to mature and do not exhibit a collecting vessel phenotype. Furthermore, dermal lymphatic vessels in Ang2−/− pups prematurely recruit smooth muscle cells and do not undergo proper postnatal remodeling. In contrast, Ang2 knock-out Ang1 knock-in mice do develop a hierarchal lymphatic vasculature, suggesting that activation of Tie-2 is required for normal lymphatic development. Taken together, this work pinpoints a specific lymphatic defect of Ang2−/− mice and further defines the sequential steps in lymphatic vessel remodeling.

An inflammation-induced mechanism for leukocyte transmigration across lymphatic vessel endothelium.

The exit of antigen-presenting cells and lymphocytes from inflamed skin to afferent lymph is vital for the initiation and maintenance of dermal immune responses. How such an exit is achieved and how cells transmigrate the distinct endothelium of lymphatic vessels are unknown. We show that inflammatory cytokines trigger activation of dermal lymphatic endothelial cells (LECs), leading to expression of the key leukocyte adhesion receptors intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), and E-selectin, as well as a discrete panel of chemokines and other potential regulators of leukocyte transmigration. Furthermore, we show that both ICAM-1 and VCAM-1 are induced in the dermal lymphatic vessels of mice exposed to skin contact hypersensitivity where they mediate lymph node trafficking of dendritic cells (DCs) via afferent lymphatics. Lastly, we show that tumor necrosis factor α stimulates both DC adhesion and transmigration of dermal LEC monolayers in vitro and that the process is efficiently inhibited by ICAM-1 and VCAM-1 adhesion-blocking monoclonal antibodies. These results reveal a CAM-mediated mechanism for recruiting leukocytes to the lymph nodes in inflammation and highlight the process of lymphatic transmigration as a potential new target for antiinflammatory therapy.

Expression of the self-marker CD47 on dendritic cells governs their trafficking to secondary lymphoid organs

Dendritic cells (DCs) capture and process Ag in the periphery. Thus, traffic through lymphatic vessels is mandatory before DCs relocate to lymph nodes where they are dedicated to T-cell priming. Here, we show that the ubiquitous self-marker CD47 selectively regulates DC, but not T and B cell trafficking across lymphatic vessels and endothelial barriers in vivo. We find an altered skin DC migration and impaired T-cell priming in CD47-deficient mice at steady state and under inflammatory conditions. Competitive DC migration assays and active immunization with myeloid DCs demonstrate that CD47 expression is required on DCs but not on the endothelium for efficient DC trafficking and T-cell responses. This migratory defect correlates with the quasi-disappearance of splenic marginal zone DCs in nonmanipulated CD47-deficient mice. Nonetheless, CCR7 expression and CCL19-driven chemotaxis remain intact. Our data reveal that CD47 on DCs is a critical factor in controlling migration and efficient initiation of the immune response.

Of mice and men; the translational physiology of a genetic form of lymphoedema

Of mice and men; the translational physiology of a genetic form of lymphoedema