Langerhans cell | |
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Details | |
System | Immune system |
Location | Skin and mucosa |
Function | Dendritic cell |
Identifiers | |
MeSH | D007801 |
FMA | 63072 |
Anatomical terms of microanatomy |
A Langerhans cell (LC) is a tissue-resident macrophage of the skin [2] once thought to be a resident dendritic cell. [3] These cells contain organelles called Birbeck granules. They are present in all layers of the epidermis and are most prominent in the stratum spinosum. [4] They also occur in the papillary dermis, particularly around blood vessels, [4] as well as in the mucosa of the mouth, foreskin, and vaginal epithelium. [5] They can be found in other tissues, such as lymph nodes, particularly in association with the condition Langerhans cell histiocytosis (LCH).
In skin infections, the local Langerhans cells take up and process microbial antigens to become fully functional antigen-presenting cells. [6]
Generally, tissue-resident macrophages are involved in immune homeostasis and the uptake of apoptotic bodies. However, Langerhans cells can also take on a dendritic cell-like phenotype and migrate to lymph nodes to interact with naive T-cells.[ medical citation needed ]
Matrix metalloproteinase is important and necessary for langerhans cell when it passes stratum basale. [7]
Langerhans cells derive from primitive erythro-myeloid progenitors that arise in the yolk sac outside the embryo in the first trimester of pregnancy, and under normal circumstances persist throughout life, being replenished by local proliferation as necessary. If the skin becomes severely inflamed, perhaps because of infection, blood monocytes are recruited to the affected region and differentiate into replacement LCs. [8]
Langerin is a protein found in Langerhans cells, [9] and dendritic cells. [10]
LCs contain a large amount of cannabinoid receptor type 2 (CB2), that by activation by agonists, attenuate both the recruitment of eosinophils and ear swelling in chronic contact dermatitis induced by repeated challenge. [11]
In the rare disease Langerhans cell histiocytosis (LCH), an excess of cells similar to these cells are produced. However LCH cells stain positive to CD14 which is a monocyte marker and shows a different, hematopoietic origin for the disorder. [12] LCH can cause damage to skin, bone and other organs.[ citation needed ]
Langerhans cells may be initial cellular targets in the sexual transmission of HIV, [13] and may be a target, reservoir, and vector of dissemination. [14] Langerhans cells have been observed in foreskin, vaginal, and oral mucosa of humans; the lower concentrations in oral mucosa suggest that it is not a likely source of HIV infection relative to foreskin and vaginal mucosa. [5]
High-risk human papillomaviruses (HPV) are sexually transmitted viruses causally associated with several cancers including cervical, vaginal, anal, and head and neck cancers that cause significant morbidity and mortality worldwide. [15] [16] [17] [18] Over half of all cervical cancer cases are associated with HPV16, the most common of the cancer-causing high-risk genotypes. [19] During its natural life cycle, HPV16 infects the basal cells of the epithelium and interacts with Langerhans cells within the epithelial layer, [20] which are responsible for initiating immune responses against epithelial invading pathogens. [21] However, HPV does not activate Langerhans cells in vitro, and this may represent a key mechanism by which HPV evades immune detection in vivo. [22] [23] [24] [25] Specifically, HPV16 entry into Langerhans cells via the annexin A2/S100A10 heterotetramer results in suppressive signaling and lack of Langerhans cell-mediated immune responses. [26] This Langerhans cell-targeted immune escape mechanism seems to be conserved among different HPV genotypes enabling these viruses to remain undetected in the absence of other inflammatory events. [27] T cells exposed to these inactivated Langerhans cells are not anergic, and can be activated against HPV upon receiving the appropriate stimuli at a later time point. [28]
It was demonstrated that Langerhans cells in HPV-induced cervical lesions were spherical, lacked dendrites, and secreted the suppressive cytokine IL-10 in vivo. [29] The authors further demonstrated that the number of IL-10 secreting immunosuppressive Langerhans cells, and the amount of IL-10 produced in lesions, corresponded with the severity of histopathology and HPV viral load, providing evidence of an active immunosuppressive mechanism employed by HPV that targets Langerhans cells in vivo.[ citation needed ]
Langerhans cells are also the initial target of the virus that causes dengue fever during its development. [30]
During ageing the capacity of Langerhans cells to migrate declines. [31] This compromises immunity and exposes the skin to infectious diseases and cancer.[ citation needed ]
Langerhans cells are named after Paul Langerhans, a German physician and anatomist, who discovered the cells at the age of 21 while he was a medical student. [32] Because of their dendrite-like appearance, he mistakenly identified the cells as part of the nervous system. [33]
A DNA vaccine is a type of vaccine that transfects a specific antigen-coding DNA sequence into the cells of an organism as a mechanism to induce an immune response.
Human papillomavirus infection is caused by a DNA virus from the Papillomaviridae family. Many HPV infections cause no symptoms and 90% resolve spontaneously within two years. In some cases, an HPV infection persists and results in either warts or precancerous lesions. These lesions, depending on the site affected, increase the risk of cancer of the cervix, vulva, vagina, penis, anus, mouth, tonsils, or throat. Nearly all cervical cancer is due to HPV, and two strains – HPV16 and HPV18 – account for 70% of all cases. HPV16 is responsible for almost 90% of HPV-positive oropharyngeal cancers. Between 60% and 90% of the other cancers listed above are also linked to HPV. HPV6 and HPV11 are common causes of genital warts and laryngeal papillomatosis.
Langerhans cell histiocytosis (LCH) is an abnormal clonal proliferation of Langerhans cells, abnormal cells deriving from bone marrow and capable of migrating from skin to lymph nodes.
Cervical intraepithelial neoplasia (CIN), also known as cervical dysplasia, is the abnormal growth of cells on the surface of the cervix that could potentially lead to cervical cancer. More specifically, CIN refers to the potentially precancerous transformation of cells of the cervix.
A histiocytoma in the dog is a benign tumor. It is an abnormal growth in the skin of histiocytes (histiocytosis), a cell that is part of the immune system. A similar disease in humans, Hashimoto-Pritzker disease, is also a Langerhans cell histiocytosis. Dog breeds that may be more at risk for this tumor include Bulldogs, American Pit Bull Terriers, American Staffordshire Terriers, Scottish Terriers, Greyhounds, Boxers, and Boston Terriers. They also rarely occur in goats and cattle.
Toll-like receptor 2 also known as TLR2 is a protein that in humans is encoded by the TLR2 gene. TLR2 has also been designated as CD282. TLR2 is one of the toll-like receptors and plays a role in the immune system. TLR2 is a membrane protein, a receptor, which is expressed on the surface of certain cells and recognizes foreign substances and passes on appropriate signals to the cells of the immune system.
Langerin (CD207) is a type II transmembrane protein which is encoded by the CD207 gene in humans. It was discovered by scientists Sem Saeland and Jenny Valladeau as a main part of Birbeck granules. Langerin is C-type lectin receptor on Langerhans cells (LCs) and in mice also on dermal interstitial CD103+ dendritic cells (DC) and on resident CD8+ DC in lymph nodes.
Margaret Anne Stanley, OBE FMedSc, is a British virologist and epithelial biologist. She attended the Universities of London, Bristol, and Adelaide. As of 2018, she is an Emeritus Professor of Epithelial Biology in the Department of Pathology at the University of Cambridge and a Fellow of the Academy of Medical Sciences. She is also an Honorary Fellow of the UK Royal College of Obstetricians and Gynaecologists and an honorary fellow of Christ's College, Cambridge. Stanley is a research scientist in virology focusing on the human papillomavirus (HPV). Her research work has led to new scientific findings on HPV. Additionally, she uses her expertise on HPV to serve on multiple advisory committees and journal editorial boards.
Toll-like receptor 5, also known as TLR5, is a protein which in humans is encoded by the TLR5 gene. It is a member of the toll-like receptor (TLR) family. TLR5 is known to recognize bacterial flagellin from invading mobile bacteria. It has been shown to be involved in the onset of many diseases, including Inflammatory bowel disease due to the high expression of TLR in intestinal lamina propria dendritic cells. Recent studies have also shown that malfunctioning of TLR5 is likely related to rheumatoid arthritis, osteoclastogenesis, and bone loss. Abnormal TLR5 functioning is related to the onset of gastric, cervical, endometrial and ovarian cancers.
Chronic multifocal Langerhans cell histiocytosis, previously known as Hand–Schüller–Christian disease, is a type of Langerhans cell histiocytosis (LCH), which can affect multiple organs. The condition is traditionally associated with a combination of three features; bulging eyes, breakdown of bone, and diabetes insipidus, although around 75% of cases do not have all three features. Other features may include a fever and weight loss, and depending on the organs involved there may be rashes, asymmetry of the face, ear infections, signs in the mouth and the appearance of advanced gum disease. Features relating to lung and liver disease may occur.
Immunosenescence is the gradual deterioration of the immune system, brought on by natural age advancement. A 2020 review concluded that the adaptive immune system is affected more than the innate immune system. Immunosenescence involves both the host's capacity to respond to infections and the development of long-term immune memory. Age-associated immune deficiency is found in both long- and short-lived species as a function of their age relative to life expectancy rather than elapsed time.
Toll-like receptor 9 is a protein that in humans is encoded by the TLR9 gene. TLR9 has also been designated as CD289. It is a member of the toll-like receptor (TLR) family. TLR9 is an important receptor expressed in immune system cells including dendritic cells, macrophages, natural killer cells, and other antigen presenting cells. TLR9 is expressed on endosomes internalized from the plasma membrane, binds DNA, and triggers signaling cascades that lead to a pro-inflammatory cytokine response. Cancer, infection, and tissue damage can all modulate TLR9 expression and activation. TLR9 is also an important factor in autoimmune diseases, and there is active research into synthetic TLR9 agonists and antagonists that help regulate autoimmune inflammation.
C-C chemokine receptor type 7 is a protein that in humans is encoded by the CCR7 gene. Two ligands have been identified for this receptor: the chemokines ligand 19 (CCL19/ELC) and ligand 21 (CCL21). The ligands have similar affinity for the receptor, though CCL19 has been shown to induce internalisation of CCR7 and desensitisation of the cell to CCL19/CCL21 signals. CCR7 is a transmembrane protein with 7 transmembrane domains, which is coupled with heterotrimeric G proteins, which transduce the signal downstream through various signalling cascades. The main function of the receptor is to guide immune cells to immune organs by detecting specific chemokines, which these tissues secrete.
Chemokine receptor 6 also known as CCR6 is a CC chemokine receptor protein which in humans is encoded by the CCR6 gene. CCR6 has also recently been designated CD196. The gene is located on the long arm of Chromosome 6 (6q27) on the Watson (plus) strand. It is 139,737 bases long and encodes a protein of 374 amino acids.
CD83 is a human protein encoded by the CD83 gene.
Lymphocyte-activation gene 3, also known as LAG-3, is a protein which in humans is encoded by the LAG3 gene. LAG3, which was discovered in 1990 and was designated CD223 after the Seventh Human Leucocyte Differentiation Antigen Workshop in 2000, is a cell surface molecule with diverse biological effects on T cell function but overall has an immune inhibitory effect. It is an immune checkpoint receptor and as such is the target of various drug development programs by pharmaceutical companies seeking to develop new treatments for cancer and autoimmune disorders. In soluble form it is also being developed as a cancer drug in its own right.
Langerhans cell sarcoma (LCS) is a rare form of malignant histiocytosis. It should not be confused with Langerhans cell histiocytosis, which is cytologically benign. It can present most commonly in the skin and lymphatic tissue, but may also present in the lung, liver, and bone marrow. Treatment is most commonly with surgery or chemotherapy.
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Jean Sylvia Marshall, born in Birmingham, England, is a Canadian immunologist and acting Professor and Head of the Department of Microbiology & Immunology at Dalhousie University in Halifax, Nova Scotia, Canada. Marshall's work has investigated how mast cells are involved in the early immune response to infection and antigen. She is best known for her discovery of the previously unknown degranulation-independent immunoregulatory roles of mast cells in infection and allergy and their ability to mobilize dendritic cells.
Miram Merad is a French-Algerian professor in Cancer immunology and the Director of the Marc and Jennifer Lipschultz Precision Immunology Institute (PrIISM) at the Icahn School of Medicine at Mount Sinai (ISMMS) in New York, NY. She is the corecipient of the 2018 William B. Coley Award for Distinguished Research in Basic Immunology and a member of the United States National Academy of Sciences and the National Academy of Medicine.