User talk:Zeeladeshra/sandbox

The lymphatic endothelium is a specialized form of epithelium and is found lining the vasculature of the lymphatic system. The first study of a pure culture of lymphatic endothelial cells can be dated back to the early 1980s, where lymphatic endothelial cells from a patient were isolated.

Structure

The lymphatic endothelium contains flattened endothelial cells, which are also characterized as simple squamous cells. The characteristics of these endothelial cells is crucial in helping the lymphatic system carry out its function as a system involved in the absorption of tissue fluids and particles. In contrast to blood capillaries, lymphatic vessels have wider lumens to accommodate for the large influx of fluids and particles across the endothelium.

The lymphatic endothelium contains many overlapping intercellular junctions due to the superimposition of the lymphatic endothelial cells. These junctions allow for the efficient flow of tissue fluids and particles through the endothelium.

The pressure gradient across the endothelium allows for the opening and closing of these intercellular junctions. When there is an increase in interstitial fluid pressure, the junctions of the lymphatic endothelium will open and allow fluids and particles to flow through the lymphatic endothelium and into the lumen of the lymphatic vessels. As the fluid enters the lumen of the vessel, the interstitial fluid pressure will decrease and cause the intercellular junctions to close, preventing any retrograde flow of fluids and particles back out into the interstitial space.

Function

Immunological Response

The lymphatic vessels allow for leukocytes to be recruited from their peripheral sites and trafficked to their respective draining lymph nodes. As such, the lymphatic endothelium which lines the lymphatic vessels plays a crucial role in both the adaptive immune response as well as the innate immune response. The lymphatic endothelial cells ensure that cellular mediators of the immune response are brought to the lymph vessels and drained effectively into the lymph nodes.

Lymphatic endothelial cells are able to express chemokines on their surface, which will attract certain cellular mediators of the innate immune response, such as dendritic cells, monocytes, basophils and neutrophils. CCL21 is a specific chemokine that is expressed by lymphatic endothelial cells, this chemokine attracts dendritic cells. Dendritic cells have a receptor on their surface called CCR7, which will bind to the CCL21 chemokine that is expressed on the lymphatic endothelial cell.

An antigen-specific adaptive immune response allows for the upregulation of certain cell adhesion molecules such as, ICAM-1 and E-selectin. These cell adhesion molecules are also expressed on lymphatic endothelial cells. The upregulation of these cell adhesion molecules is synergistic with the expression of chemokines like CCL21 on the surface of lymphatic endothelial cells. All of these processes together, will recruit cellular mediators like dendritic cells towards the lymph vessels. Once recruited, the cellular mediators are able to transmigrate across the lymphatic endothelial cells and move towards the lymph nodes through the help of cell adhesion molecules. This process is crucial during antigenic challenges that arise in the body, as it creates an efficient and effective immune response.

Further reading

• Jackson DG (2003). "The lymphatics revisited: new perspectives from the hyaluronan receptor LYVE-1". Trends Cardiovasc. Med. 13 (1): 1–7. doi:10.1016/S1050-1738(02)00189-5. PMID 12554094.
• Banerji S, Ni J, Wang SX, et al. (1999). "LYVE-1, a new homologue of the CD44 glycoprotein, is a lymph-specific receptor for hyaluronan". J. Cell Biol. 144 (4): 789–801. doi:10.1083/jcb.144.4.789. PMC 2132933Freely accessible. PMID 10037799.
• Cunnick GH, Jiang WG, Gomez KF, Mansel RE (2001). "Lymphangiogenesis quantification using quantitative PCR and breast cancer as a model". Biochem. Biophys. Res. Commun. 288 (4): 1043–1046. doi:10.1006/bbrc.2001.5869. PMID 11689016.
• Mouta Carreira C, Nasser SM, di Tomaso E, et al. (2001). "LYVE-1 is not restricted to the lymph vessels: expression in normal liver blood sinusoids and down-regulation in human liver cancer and cirrhosis". Cancer Res. 61 (22): 8079–84. PMID 11719431.
• Cursiefen C, Schlötzer-Schrehardt U, Küchle M, et al. (2002). "Lymphatic vessels in vascularized human corneas: immunohistochemical investigation using LYVE-1 and podoplanin". Invest. Ophthalmol. Vis. Sci. 43 (7): 2127–35. PMID 12091407.
• Strausberg RL, Feingold EA, Grouse LH, et al. (2003). "Generation and initial analysis of more than 15,000 full-length human and mouse cDNA sequences". Proc. Natl. Acad. Sci. U.S.A. 99 (26): 16899–16903. doi:10.1073/pnas.242603899. PMC 139241Freely accessible. PMID 12477932.
• Huang SS, Tang FM, Huang YH, et al. (2003). "Cloning, expression, characterization, and role in autocrine cell growth of cell surface retention sequence binding protein-1". J. Biol. Chem. 278 (44): 43855–43869. doi:10.1074/jbc.M306411200. PMID 12912978.
• Clark HF, Gurney AL, Abaya E, et al. (2003). "The secreted protein discovery initiative (SPDI), a large-scale effort to identify novel human secreted and transmembrane proteins: a bioinformatics assessment". Genome Res. 13 (10): 2265–2270. doi:10.1101/gr.1293003. PMC 403697Freely accessible. PMID 12975309.
• Gerhard DS, Wagner L, Feingold EA, et al. (2004). "The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC)". Genome Res. 14 (10B): 2121–2127. doi:10.1101/gr.2596504. PMC 528928Freely accessible. PMID 15489334.
• Otsuki T, Ota T, Nishikawa T, et al. (2007). "Signal sequence and keyword trap in silico for selection of full-length human cDNAs encoding secretion or membrane proteins from oligo-capped cDNA libraries". DNA Res. 12 (2): 117–126. doi:10.1093/dnares/12.2.117. PMID 16303743.
• Liu T, Qian WJ, Gritsenko MA, et al. (2006). "Human plasma N-glycoproteome analysis by immunoaffinity subtraction, hydrazide chemistry, and mass spectrometry". J. Proteome Res. 4 (6): 2070–2080. doi:10.1021/pr0502065. PMC 1850943Freely accessible. PMID 16335952.
• Kimura K, Wakamatsu A, Suzuki Y, et al. (2006). "Diversification of transcriptional modulation: large-scale identification and characterization of putative alternative promoters of human genes". Genome Res. 16 (1): 55–65. doi:10.1101/gr.4039406. PMC 1356129Freely accessible. PMID 16344560.
• Nguyen VA, Kutzner H, Fürhapter C, et al. (2006). "Infantile hemangioma is a proliferation of LYVE-1-negative blood endothelial cells without lymphatic competence". Mod. Pathol. 19 (2): 291–298. doi:10.1038/modpathol.3800537. PMID 16424896.
• Gu B, Alexander JS, Gu Y, et al. (2007). "Expression of lymphatic vascular endothelial hyaluronan receptor-1 (LYVE-1) in the human placenta". Lymphatic research and biology. 4 (1): 11–17. doi:10.1089/lrb.2006.4.11. PMC 3072054Freely accessible. PMID 16569201.
• Llovet JM, Chen Y, Wurmbach E, et al. (2007). "A molecular signature to discriminate dysplastic nodules from early hepatocellular carcinoma in HCV cirrhosis". Gastroenterology. 131 (6): 1758–1767. doi:10.1053/j.gastro.2006.09.014. PMID 17087938.Small text