Adaptive Tumor Suppression
John Melford in Pocket Guide to Cancer, 2017
Dendritic cells get their name from their surface projections that resemble the dendrites of neurons, a type of cell used to relay messages in the nervous system. Immature dendritic cells are produced in the bone marrow from where they migrate throughout the body. They remain dormant until they encounter invading pathogens or molecules of foreign origin, which they engulf, process, and present. Dendritic cells are found in most tissues of the body and are particularly abundant in areas where they are more likely to encounter antigens such as the skin, lungs, and gastrointestinal tract. Although macrophages also present antigens, dendritic cells are better at it, and often are described as professional antigen‑presenting cells. For this function, dendritic cells have an enhanced capability to uptake antigens and process them for presentation on their outer cell membrane. Macrophages and dendritic cells use both MHC Class I and MHC Class II molecules to present antigens. Other cells of the body use just MHC Class I molecules. Dendritic cells also help to control the function of T-cells and other types of lymphocytes.
Arenaviruses and Neurovirology
Sunit K. Singh, Daniel Růžek in Neuroviral Infections, 2013
As discussed in the sections regarding rodent and human infection, the manifestations of LCM infection can be quite varied, especially in rodents whether self-limited or chronic infection occurs. Quite subtle changes in the glycoprotein of LCM have been shown to be part of the cause of persistence of LCM, as studied in dendritic cells. Dendritic cells are present in tissues in contact with the external environment, such as the skin (where there is a specialized dendritic cell type called Langerhans cells), and the inner lining of the nose, lungs, stomach, and intestines. As an example, LCM clone 13 infection, which results in persistence, and differs from the standard Armstrong strain only by few nucleotides, three of which result in coding changes (Sullivan et al. 2011), two in GP1 and one in the RNA-dependent RNA polymerase. The GP1 changes (especially F260L) mediate exceptionally strong binding affinity to the LCM cellular receptor, alpha-dystroglycan. This effect on dendritic cells results in decreased amounts of costimulatory ligands, an inability to fully prime T cells, up-regulation of T-cell inhibitory receptors, and difficulties in viral clearance of LCM. Alternative receptors have also been described for LCM virus (Kunz et al. 2004), which do not produce immune suppression. A number of the New World arenaviruses can use human transferring receptor 1 as a cellular receptor (Radoshitzky et al. 2007).
Basic science
Declan Costello, Guri Sandhu in Practical Laryngology, 2015
Virtually all types of immune cells have been identified in the larynx and are distributed throughout the mucosa and lamina propria. The exception is the highly organised lymphoid collections, which are similar to Peyer’s patches and are located predominantly in the supraglottic area. Dendritic cells have been heavily investigated owing to the roles they play in antigen presentation and immune response initiation. Dense populations of dendritic cells exist in the larynx, mainly around the basal membrane where dendrites extend through the mucosal layers. Helper and cytotoxic T cells are concentrated in the lamina propria and the MHC class I-rich deeper layer of the epithelium. This distribution seems logical, as these T cells recognise antigens presented by the MHC class molecules. Insults to laryngeal mucosa, such as tobacco smoking and laryngopharyngeal reflux, change the immunological composition and function of the mucosa.
Galangin ameliorates experimental autoimmune encephalomyelitis in mice via modulation of cellular immunity
Published in Journal of Immunotoxicology, 2021
Kok-Tong Tan, Shiming Li, Lauren Panny, Chi-Chien Lin, Shih-Chao Lin
Dendritic cells (DC) play a crucial role in modulating and orchestrating human immune responses, particularly cellular immunity. In the context of MS pathogenesis, DC could trigger auto-reactive T-cell responses via presentation of myelin-derived epitopes and through secretion of cytokines that polarize T-cell differentiation into T-helper (TH)-1 and TH17 cells (Fletcher et al. 2010). Myelin-reactive T-cells migrate from the peripheral tissue to the CNS where they are reactivated by resident antigen-presenting cells (APC) like microglial cells and astrocytes. Upon activation, these APC release more pro-inflammatory cytokines, such as interferon (IFN)-γ and interleukin (IL)-17, ultimately resulting in the continuing damage to/destruction of the myelin on axons (Wang et al. 2018).
What is the fertility-enhancing effect of tubal flushing? A hypothesis article
Published in Journal of Obstetrics and Gynaecology, 2022
Inez Roest, Amir M. Hajiyavand, Marlies Y. Bongers, Velja Mijatovic, Ben Willem J. Mol, Carolien A. M. Koks, Karl D. Dearn
A 1987 rodent study showed the induction of decidua formation after intrauterine oil injection in appropriately sensitised uteri (Milligan 1987). Later research in a mouse model, showed that CD205+ dendritic cells decrease after the instillation of oil-based contrast, compared with sham and saline infusion treatments. Dendritic cells present antigens and thereby stimulate the T-cells of the immune system. The decrease in these cells reduces antigen sampling and the immune system’s presenting capability in the uterus. The fertility-enhancing mechanism of oil-based contrast may be via damping the immune response to antigens, including a conceptus. Two hypotheses for the decrease in dendritic cells after oil-based contrast injection are; a toxic effect on the dendritic cells or stimulation of dendritic cells’s migration to lymphoid organs (Johnson et al. 2005).
Immunopathology of COVID-19 and its implications in the development of rhino-orbital-cerebral mucormycosis: a major review
Published in Orbit, 2022
Tarjani Vivek Dave, Akshay Gopinathan Nair, Joveeta Joseph, Suzanne K Freitag
Platelets are one of the key cells in the innate immune response. While their primary role is in hemostasis, another important role is in the immune response against pathogens, by inhibiting their dissemination through the circulation, which could increase the severity of infection.46 Platelets help in fighting microbes by producing antimicrobial peptides such as platelet factor 4.47 Typical hematologic features of COVID-19 include thrombocytopenia, lymphopenia, and neutrophilia.48 NK cells modulate the immune response that is mounted when a pathogen is encountered. There is a reduction in the number of NK cells and blunting of the effector functions of NK cells in COVID-19.46 This results in a decrease in the clearance of infected and activated cells and also results in an unabated elevation of toxic inflammatory markers.46 Previous literature has clearly shown that SARS-CoV can cause infection of the dendritic cells (DC). This can lead to an upregulation of inflammatory chemokines following a very poor antiviral cytokine expression.49,50 Dendritic cells play a prime role in specific T-cell responses, cytokine production, and antigen presentation.49 In patients with COVID-19, a loss of DC function could lead to delayed response of the immune system.
Related Knowledge Centers
- Adaptive Immune System
- Antigen Presentation
- Innate Immune System
- Langerhans Cell
- Immune System
- Skin
- T Cell
- Antigen
- Antigen-Presenting Cell
- Nose