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Concept: Lymphatic system


Confocal laser endomicroscopy (pCLE) provides real-time histologic imaging of human tissues at a depth of 60-70 μm during endoscopy. pCLE of the extrahepatic bile duct after fluorescein injection demonstrated a reticular pattern within fluorescein-filled sinuses that had no known anatomical correlate. Freezing biopsy tissue before fixation preserved the anatomy of this structure, demonstrating that it is part of the submucosa and a previously unappreciated fluid-filled interstitial space, draining to lymph nodes and supported by a complex network of thick collagen bundles. These bundles are intermittently lined on one side by fibroblast-like cells that stain with endothelial markers and vimentin, although there is a highly unusual and extensive unlined interface between the matrix proteins of the bundles and the surrounding fluid. We observed similar structures in numerous tissues that are subject to intermittent or rhythmic compression, including the submucosae of the entire gastrointestinal tract and urinary bladder, the dermis, the peri-bronchial and peri-arterial soft tissues, and fascia. These anatomic structures may be important in cancer metastasis, edema, fibrosis, and mechanical functioning of many or all tissues and organs. In sum, we describe the anatomy and histology of a previously unrecognized, though widespread, macroscopic, fluid-filled space within and between tissues, a novel expansion and specification of the concept of the human interstitium.

Concepts: Cancer, Biology, Lymph node, Liver, Histology, Lymphatic system, Anatomy, Human anatomy


The increasing prevalence of tattoos provoked safety concerns with respect to particle distribution and effects inside the human body. We used skin and lymphatic tissues from human corpses to address local biokinetics by means of synchrotron X-ray fluorescence (XRF) techniques at both the micro (μ) and nano (ν) scale. Additional advanced mass spectrometry-based methodology enabled to demonstrate simultaneous transport of organic pigments, heavy metals and titanium dioxide from skin to regional lymph nodes. Among these compounds, organic pigments displayed the broadest size range with smallest species preferentially reaching the lymph nodes. Using synchrotron μ-FTIR analysis we were also able to detect ultrastructural changes of the tissue adjacent to tattoo particles through altered amide I α-helix to β-sheet protein ratios and elevated lipid contents. Altogether we report strong evidence for both migration and long-term deposition of toxic elements and tattoo pigments as well as for conformational alterations of biomolecules that likely contribute to cutaneous inflammation and other adversities upon tattooing.

Concepts: Oxygen, Lymph node, Lymphatic system, Skin, Tissue, Titanium dioxide, Heavy metal music, Tattoo


Here, we report the existence of meningeal lymphatic vessels in human and nonhuman primates (common marmoset monkeys) and the feasibility of noninvasively imaging and mapping them in vivo with high-resolution, clinical MRI. On T2-FLAIR and T1-weighted black-blood imaging, lymphatic vessels enhance with gadobutrol, a gadolinium-based contrast agent with high propensity to extravasate across a permeable capillary endothelial barrier, but not with gadofosveset, a blood-pool contrast agent. The topography of these vessels, running alongside dural venous sinuses, recapitulates the meningeal lymphatic system of rodents. In primates, meningeal lymphatics display a typical panel of lymphatic endothelial markers by immunohistochemistry. This discovery holds promise for better understanding the normal physiology of lymphatic drainage from the central nervous system and potential aberrations in neurological diseases.

Concepts: Inflammation, Central nervous system, Nervous system, Brain, Lymphatic system, Cardiovascular system, Primate


The administration of interleukin 33 and deletion of IL-33 receptor, ST2 molecule, affects the induction of autoimmunity in different experimental models of human autoimmune diseases. The aim of this study was to analyze the effect of ST2 deletion on the induction of experimental autoimmune encephalomyelitis (EAE) in resistant BALB/c mice. Mice were immunized with MOG(35-55) peptide or disease was induced by passive transfer of encephalitogenic singenic cells and EAE was clinically and histologically evaluated. Expression of intracellular inflammatory cytokines, markers of activation and chemokine receptors on lymphoid tissue and CNS infiltrating mononuclear cells was analyzed by flow cytometry. We report here that deletion of ST2(-/-) molecule abrogates resistance of BALB/c mice to EAE induction based on clinical and histopathological findings. Brain and spinal cord infiltrates of ST2(-/-) mice had significantly higher number of CD4(+) T lymphocytes containing inflammatory cytokines compared to BALB/c WT mice. Adoptive transfer of ST2(-/-) primed lymphocytes induced clinical signs of the disease in ST2(-/-) as well as in WT mice. MOG(35-55) restimulated ST2(-/-) CD4(+) cells as well as ex vivo analyzed lymph node cells had higher expression of T-bet and IL-17, IFN-γ, TNF-α and GM-CSF in comparison with WT CD4(+) cells. ST2(-/-) mice had higher percentages of CD4(+) cells expressing chemokine receptors important for migration to CNS in comparison with WT CD4(+) cells. Draining lymph nodes of ST2(-/-) mice contained higher percentage of CD11c(+)CD11b(+)CD8(-) cells containing inflammatory cytokines IL-6 and IL-12 with higher expression of activation markers. Transfer of ST2(-/-) but not WT dendritic cells induced EAE in MOG(35-55) immunized WT mice. Our results indicate that ST2 deficiency attenuates inherent resistance of BALB/c mice to EAE induction by enhancing differentiation of proinflammatory antigen presenting cells and consecutive differentiation of encephalitogenic T cells in the draining lymph node rather than affecting their action in the target tissue.

Concepts: Immune system, Inflammation, Lymph node, Lymphatic system, Interleukin, Dendritic cell, Lymph, Lymph vessel


Tetraspanins have emerged as key players in malignancy and inflammatory diseases, yet little is known about their roles in angiogenesis, and nothing about their involvement in lymphangiogenesis. We here found that tetraspanins are abundantly expressed in human lymphatic endothelial cells (LEC) and tumor LECs. After intrathoracic tumor implantation, metastasis to lymph nodes was diminished and accompanied by decreased angiogenesis and lymphangiogenesis in tetraspanin CD9 Knockout (KO) mice. Moreover, lymphangiomas induced in CD9-KO mice were less pronounced with decreased lymphangiogenesis when compared with wild-type mice. While mouse LEC isolated from CD9-KO mice showed normal adhesion, lymphangiogenesis was markedly impaired in several assays (migration, proliferation, and cable formation) in vitro, and in the lymphatic ring assay ex vivo. Consistent with these findings in mouse LEC, knocking down of CD9 in human LEC also showed decreased migration, proliferation, and cable formation. Immunoprecipitation analysis demonstrated that deletion of CD9 in LEC diminished functional complexes between vascular endothelial growth factor receptor (VEGFR)-3, and integrins (α5 and α9). Therefore, knocking down of CD9 in LEC attenuated VEGFR-3 signaling as well as down-stream signaling such as Erk, and p38 upon VEGF-C stimulation. Finally, double-deletion of CD9/CD81 in mice exhibited abnormal development of lymphatic vasculature in the trachea and diaphragm, suggesting that CD9 and a closely related tetraspanin CD81 coordinately play an essential role in physiological lymphangiogenesis. In conclusion, tetraspanin CD9 modulate molecular organization of integrins in LEC, thereby supporting several functions required for lymphangiogenesis.

Concepts: Inflammation, Angiogenesis, Blood vessel, Vascular endothelial growth factor, In vivo, Lymphatic system, In vitro, CD9


BACKGROUND: Since the introduction of sentinel lymph node biopsy (SLNB), its use as a standard of care for patients with clinically node-negative cutaneous melanoma remains controversial. We wished to evaluate our experience of SLNB for melanoma. METHODS: A single center observational cohort of 203 melanoma patients with a primary cutaneous melanoma (tumour thickness > 1 mm) and without clinical evidence of metastasis was investigated from 2002 to 2009. Head and neck melanoma were excluded. SLN was identified following preoperative lymphoscintigraphy and intraoperative gamma probe interrogation. RESULTS: The SLN identification rate was 97%. The SLN was tumor positive in 44 patients (22%). Positive SLN was significantly associated with primary tumor thickness and microscopic ulceration. The median follow-up was 39.5 (5–97) months. Disease progression was significantly more frequent in SLN positive patients (32% vs 13%, p = 0.002). Five-year DFS and OS of the entire cohort were 79.6% and 84.6%, respectively, with a statistical significant difference between SLN positive (58.7% and 69.7%) and SLN negative (85% and 90.3%) patients (p = 0.0006 and p = 0.0096 respectively). Postoperative complications after SLNB were observed in 12% of patients. CONCLUSION: Our data confirm previous studies and support the clinical usefulness of SLNB as a reliable and accurate staging method in patients with cutaneous melanoma. However, the benefit of additional CLND in patients with positive SLN remains to be demonstrated.

Concepts: Cancer, Breast cancer, Metastasis, Oncology, Lymphatic system, Sentinel lymph node, Lymph node biopsy, Gamma Probe


An adult female long-beaked common dolphin Delphinus capensis live-stranded in La Jolla, California, USA, on July 30, 2012 and subsequently died on the beach. Computed tomography and magnetic resonance imaging revealed gas bubble accumulation in the vasculature, organ parenchyma, mandibular fat pads, and subdermal sheath as well as a gas-filled cavity within the liver, mild caudal abdominal effusion, and fluid in the uterus. Gross examination confirmed these findings and also identified mild ulcerations on the palate, ventral skin, and flukes, uterine necrosis, and multifocal parenchymal cavitations in the brain. Histological review demonstrated necrosis and round clear spaces interpreted as gas bubbles with associated bacterial rods within the brain, liver, spleen, and lymph nodes. Anaerobic cultures of the lung, spleen, liver, bone marrow, and abdominal fluid yielded Clostridium perfringens, which was further identified as type A via a multiplex PCR assay. The gas composition of sampled bubbles was typical of putrefaction gases, which is consistent with the by-products of C. perfringens, a gas-producing bacterium. Gas bubble formation in marine mammals due to barotrauma, and peri- or postmortem off-gassing of supersaturated tissues and blood has been previously described. This case study concluded that a systemic infection of C. perfringens likely resulted in production of gas and toxins, causing tissue necrosis.

Concepts: Cancer, Brain, Blood, Medical imaging, Magnetic resonance imaging, Lymphatic system, Clostridium perfringens, Gases


HIV-1 infection is enhanced by adhesive structures that form between infected and uninfected T cells called virological synapses (VSs). This mode of transmission results in the frequent co-transmission of multiple copies of HIV-1 across the VS, which can reduce sensitivity to antiretroviral drugs. Studying HIV-1 infection of humanized mice, we measured the frequency of co-transmission and the spatiotemporal organization of infected cells as indicators of cell-to-cell transmission in vivo. When inoculating mice with cells co-infected with two viral genotypes, we observed high levels of co-transmission to target cells. Additionally, micro-anatomical clustering of viral genotypes within lymphoid tissue indicates that viral spread is driven by local processes and not a diffuse viral cloud. Intravital splenic imaging reveals that anchored HIV-infected cells induce arrest of interacting, uninfected CD4(+) T cells to form Env-dependent cell-cell conjugates. These findings suggest that HIV-1 spread between immune cells can be anatomically localized into infectious clusters.

Concepts: HIV, Immune system, White blood cell, Infection, Organ, Transmission and infection of H5N1, Lymphatic system, Spleen


The currently-used modes of administration of immunotherapeutic agents result in their limited delivery to the lymph nodes and/or require repetitive ultrasound-guided nodal injections or microsurgical lymphatic injections, limiting their feasibility. Here, we report on the feasibility and safety of a new method of long-term repetitive intralymphatic (IL) infusion of immune cells, using implantable delivery ports.

Concepts: Immune system, Lymph node, Lymphatic system


Chimeric Antigen Receptor (CAR) T-cells have emerged as a powerful immunotherapy for various forms of cancer and show promise in treating HIV-1 infection. However, significant limitations are persistence and whether peripheral T cell-based products can respond to malignant or infected cells that may reappear months or years after treatment remains unclear. Hematopoietic Stem/Progenitor Cells (HSPCs) are capable of long-term engraftment and have the potential to overcome these limitations. Here, we report the use of a protective CD4 chimeric antigen receptor (C46CD4CAR) to redirect HSPC-derived T-cells against simian/human immunodeficiency virus (SHIV) infection in pigtail macaques. CAR-containing cells persisted for more than 2 years without any measurable toxicity and were capable of multilineage engraftment. Combination antiretroviral therapy (cART) treatment followed by cART withdrawal resulted in lower viral rebound in CAR animals relative to controls, and demonstrated an immune memory-like response. We found CAR-expressing cells in multiple lymphoid tissues, decreased tissue-associated SHIV RNA levels, and substantially higher CD4/CD8 ratios in the gut as compared to controls. These results show that HSPC-derived CAR T-cells are capable of long-term engraftment and immune surveillance. This study demonstrates for the first time the safety and feasibility of HSPC-based CAR therapy in a large animal preclinical model.

Concepts: Antiretroviral drug, HIV, AIDS, Immune system, Protein, T helper cell, Lymphatic system, Thymus