Lymph nodes go with the flow

The lymphatic vascular system is a highly organized network of structurally and functionally connected specialized lymphatic vessels of various sizes and lymph nodes that perform metabolic and transport functions. Lymph is a blood plasma filtrate that comprises antigen-presenting cells and lymphocytes. Via lymph, excess fluid and extravasated proteins are removed from the tissues. The lymphatic system supports an extracellular fluid homeostasis that is favorable for optimal tissue functioning by removing substances that result from metabolism or cell death, as well as optimizing immunity against bacteria, viruses and other antigens. Although the lymphatic vasculature is not formally considered part of the immune system, it is crucial for the traffic of antigens and immune cells. In addition, lymphatic endothelial cells can supply antigens and express factors that modulate immune responses. After an inflammatory stimulus, endothelial cells produce chemokines, which recruit immune cells to the lymph nodes. Unlike the circulatory system with a centralized pump, the movement of lymph through the network of lymphatic vessels is provided by forces that stimulate the initial formation of lymph in the tissues and the ability of the lymphatic vessels and nodes to rhythmically contract, providing increased pressure and lymph movement in the proximal direction. Since the metabolic rate in various organs and tissues varies significantly depending on the functional state of the tissue, the blood flow through the tissue and the amount of lymph formed also change significantly. The lymphatic vasculature has several circuits for regulating lymph flow. This review provides a comprehensive overview of the important results obtained over the past century and discusses the molecular and physiological control of the transport function of lymphatic vessels and nodes.

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The olfactory organ is a unique site for resident neutrophils in the brain

10.1101/2021.07.22.453396 ◽

2021 ◽

Author(s):

Kathleen E Whitlock ◽

M. Fernanda Palominos ◽

Danissa Candia ◽

Jorge Torres-Paz

Keyword(s):

Immune Response ◽

Lymph Nodes ◽

Sensory System ◽

High Endothelial Venules ◽

Cervical Lymph Nodes ◽

Fluorescent Reporter ◽

Brdu Labeling ◽

Lymphatic Vasculature ◽

Olfactory Organs ◽

The Brain

For decades we have known that the brain "drains" through the subarachnoid space following a route that crosses the cribriform plate to the nasal mucosa and cervical lymph nodes. Yet little is known about the potential role of the olfactory epithelia and associated lymphatic vasculature in the immune response. To better understand the immune response in the olfactory organs we used cell-specific fluorescent reporter lines in dissected, intact adult brains to visualize blood-lymphatic vasculature and neutrophils in the olfactory sensory system. Here we show that the extensive blood vasculature of the olfactory organs is associated with a lymphatic cell type resembling high endothelial venules (HEVs) of the lymph nodes in mammals and a second resembling Mural Lymphatic Endothelial Cells (muLECs) that extended from the brain to the peripheral olfactory epithelia. Surprisingly, the olfactory organs contained the only neutrophil populations observed in the brain. Damage to the olfactory epithelia resulted in a rapid increase of neutrophils within the olfactory organs as well as the appearance of neutrophils in the brain suggesting that neutrophils enter the brain in response to damage. Analysis of cell division during and after damage showed an increase in BrdU labeling in the olfactory epithelia and a subset of the neutrophils. Our results reveal a unique population of neutrophils in the olfactory organs that are associated with an extensive lymphatic vasculature suggesting a dual olfactory-immune function for this unique sensory system.

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Lymphatic Endothelial Cell Activation and Dendritic Cell Transmigration Is Modified by Genetic Deletion of Clever-1

Frontiers in Immunology ◽

10.3389/fimmu.2021.602122 ◽

2021 ◽

Vol 12 ◽

Author(s):

Sina Tadayon ◽

Johannes Dunkel ◽

Akira Takeda ◽

Dominik Eichin ◽

Reetta Virtakoivu ◽

...

Keyword(s):

Dendritic Cell ◽

Immune Responses ◽

Lymph Nodes ◽

Cell Activation ◽

Lymphatic Endothelial Cell ◽

Endothelial Cell Activation ◽

Mhc Ii ◽

Lymphatic Vasculature ◽

Inflammatory Macrophages ◽

Draining Lymph Nodes

Clever-1 also known as Stabilin-1 and FEEL-1 is a scavenger molecule expressed on a subpopulation of anti-inflammatory macrophages and lymphatic endothelial cells (LECs). However, its role in regulating dendritic cell (DC) trafficking and subsequent effects on immunity have remained unexplored. In this study, we demonstrate that DC trafficking from the skin into the draining lymph nodes is compromised in the absence of Clever-1. By adoptive transfer approaches we further show that the poor trafficking is due to the impaired entrance of DCs into afferent lymphatics. Despite this, injections of ovalbumin-loaded DCs into the footpads induced a stronger proliferative response of OT II T cells in the draining lymph nodes. This could be explained by the increased MHC II expression on DCs and a less tolerogenic phenotype of LECs in lymph nodes of Clever-1 knockout mice. Thus, although fewer DCs reach the nodes, they are more active in creating antigen-specific immune responses. This suggests that the DCs migrating to the draining lymph node within Clever-1 positive lymphatics experience immunosuppressive interactions with LECs. In conclusion, besides being a trafficking molecule on lymphatic vasculature Clever-1 is immunosuppressive towards migrating DCs and thus, regulates the magnitude of immune responses created by incoming DCs in the draining lymph nodes.

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Neutrophil Interactions with the Lymphatic System

Cells ◽

10.3390/cells10082106 ◽

2021 ◽

Vol 10 (8) ◽

pp. 2106

Author(s):

Arnolda Jakovija ◽

Tatyana Chtanova

Keyword(s):

Lymph Nodes ◽

Lymphatic System ◽

Neutrophil Migration ◽

Lymphatic Vessels ◽

High Endothelial Venules ◽

Microbial Infections ◽

Lymphatic Vasculature ◽

Pathogen Control ◽

Secondary Lymphoid Organs ◽

Draining Lymph Nodes

The lymphatic system is a complex network of lymphatic vessels and lymph nodes designed to balance fluid homeostasis and facilitate host immune defence. Neutrophils are rapidly recruited to sites of inflammation to provide the first line of protection against microbial infections. The traditional view of neutrophils as short-lived cells, whose role is restricted to providing sterilizing immunity at sites of infection, is rapidly evolving to include additional functions at the interface between the innate and adaptive immune systems. Neutrophils travel via the lymphatics from the site of inflammation to transport antigens to lymph nodes. They can also enter lymph nodes from the blood by crossing high endothelial venules. Neutrophil functions in draining lymph nodes include pathogen control and modulation of adaptive immunity. Another facet of neutrophil interactions with the lymphatic system is their ability to promote lymphangiogenesis in draining lymph nodes and inflamed tissues. In this review, we discuss the significance of neutrophil migration to secondary lymphoid organs and within the lymphatic vasculature and highlight emerging evidence of the neutrophils’ role in lymphangiogenesis.

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Scanning electron microscopy of freeze-fractured prescapular lymph node of caprine

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100111331 ◽

1984 ◽

Vol 42 ◽

pp. 244-245

Author(s):

O. Faroon ◽

F. Al-Bagdadi ◽

T. G. Snider ◽

C. Titkemeyer

Keyword(s):

Lymph Node ◽

Lymph Nodes ◽

Lymphatic System ◽

Three Dimensional ◽

Meat Products ◽

The Body ◽

Morphological Data ◽

The World ◽

Cellular Constituent ◽

Scanning Electron

The lymphatic system is very important in the immunological activities of the body. Clinicians confirm the diagnosis of infectious diseases by palpating the involved cutaneous lymph node for changes in size, heat, and consistency. Clinical pathologists diagnose systemic diseases through biopsies of superficial lymph nodes. In many parts of the world the goat is considered as an important source of milk and meat products.The lymphatic system has been studied extensively. These studies lack precise information on the natural morphology of the lymph nodes and their vascular and cellular constituent. This is due to using improper technique for such studies. A few studies used the SEM, conducted by cutting the lymph node with a blade. The morphological data collected by this method are artificial and do not reflect the normal three dimensional surface of the examined area of the lymph node. SEM has been used to study the lymph vessels and lymph nodes of different animals. No information on the cutaneous lymph nodes of the goat has ever been collected using the scanning electron microscope.

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Microvasculature and structure of hemal lymph nodes in the wall of the rabbit bladder: a vascular corrosion casting and EM study

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100141743 ◽

1995 ◽

Vol 53 ◽

pp. 1074-1075

Author(s):

F.E. Hossler ◽

M.I. McKamey ◽

F.C. Monson

Keyword(s):

Lymph Nodes ◽

Light Microscopy ◽

Corrosion Casting ◽

Fixed Tissue ◽

Infusion Pressure ◽

India Ink ◽

Cacodylate Buffer ◽

Rabbit Bladder ◽

Lateral Walls ◽

Comprehensive Study

A comprehensive study of the microvasculature of the normal rabbit bladder, revealed unusual "capillary glomeruli" along the lateral walls. Here they are characterized as hemal lymph nodes using light microscopy, SEM, TEM, ink injection, and vascular casting.Bladders were perfused via a cannula placed in the abdominal aorta with either 2% glutaraldehyde in 0.1M cacodylate buffer (pH 7.4) for fixation, 10% India ink in 0.9% saline and 0.1M phosphate (pH 7.4) for vessel tracing, or resin (Mercoximethylmethacrylate: catalyst, 4:1:0.3; Ladd Research Industries) for vascular corrosion casting. Infusion pressure was 100mm Hg. Fixed tissue was sectioned from epon-araldyte resin, and stained with toluidine blue for light microscopy, and lead and uranium for TEM. Ink injected tissue was photographed directly from saline-filled bladders illuminated from below. Resin-filled tissue was macerated in 5% KOH and distilled water. Casts were critical point dried, sputter coated with goldpalladium, and examined by routine SEM at 10 KV.

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