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Animal Connection Challenges
Published in Michael Hehenberger, Zhi Xia, Huanming Yang, Our Animal Connection, 2020
Michael Hehenberger, Zhi Xia, Huanming Yang
Adaptive immune response: SARS-CoV-2 virus is ingested by an antigen-presenting cell (APC). The virus is engulfed and T-helper cells are activatedT-helper cells (also known as CD4 cells) release T cell cytokines that suppress or regulate immune responses.T cell cytokines activate B cell antibodies that can EITHER block the virus from further infecting cells, OR mark the infected cells for destruction by cytotoxic T cells.Cytotoxic T (also known as CD8 or killer) cells identify and destroy virus-infected cells.Memory and T cells recognize the virus and can monitor their attack on the body for a long time (“immunity”).
Molecular Mechanisms for Statin Pleiotropy and Possible Clinical Relevance in Cardiovascular Disease
Published in Peter Grunwald, Pharmaceutical Biocatalysis, 2020
Brian Yu, Nikola Sladojevic, James K. Liao
Statins also may inhibit T cell activation, differentiation, and function. CD4+ T helper cell activation is mediated by major histocompatibility complex class II (MHC-II) receptors and the CD40/CD40L signaling pathway. CD4+ T cells also regulate other immune functions, including activation and proliferation of cytotoxic CD8+ T cells and activity of macrophages. An important regulator of MHC-II expression is interferon-γ (IFN-γ), which causes inducible MHC-II expression through the transactivator CIITA. Statins reduce levels of IFN-γ and inhibit promoter IV of CIITA, leading to repression of MHC-II induction, CD4+ T cell activation, and subsequent pro-inflammatory processes (Kwak et al., 2001). Furthermore, statins decrease CD40 expression and CD40-related activation in vascular cells, further downregulating CD4+ T cell activation (Mulhaupt et al., 2003). Recent studies also suggest statins inhibit differentiation of pro-inflammatory CD4+ T helper 17 (Th17) cells while enhancing differentiation of Foxp3+ CD4+ T regulatory cells (Tregs), cells that inhibit effector T cells through a variety of mechanisms (Kagami et al., 2009; Kim et al., 2010). Inhibition of geranylgeranylation but not farnesylation mimicked these effects, although surprisingly, ROCK inhibitors had no effect on these processes—suggesting geranylated proteins other than RhoA may mediate the inhibition of Treg differentiation. Aside from their effects on CD4+ T cells and Tregs, statins may also reduce pathogenicity of CD8+ T cells, mediated by statin-induced increases in T cell KLF2 expression (Bu et al., 2010).
Bioartificial organs
Published in Ronald L. Fournier, Basic Transport Phenomena in Biomedical Engineering, 2017
Figure 11.4 illustrates how the CD8+ T cell becomes activated. Here, we see that the CD8+ TcR binds with the antigen/MHC class I complex presented, e.g., by a virally infected cell. Once again, the CD8 molecule stabilizes the interaction between the TcR and the antigen/MHC complex. This binding of TcR and antigen/MHC complex represents the first signal. In order for the CD8+ T cells to proliferate, i.e., form a clone of CD8+ T cells and become activated, it also must receive a second signal that is provided by the IL-2 that is released as a result of the activation of the CD4+ T cell shown in Figure 11.3. The activated CD8+ T cell will then kill any cell that expresses the appropriate combination of antigen and MHC class I. The activated CD8+ T cell accomplishes this cellular destruction through the release of special molecules called perforins that destroy the cell membranes of the target cell. Because of their role in cell death, the CD8+ T cells are also known as cytotoxic T cells or killer T cells.
Effects of life-stage and passive tobacco smoke exposure on pulmonary innate immunity and influenza infection in mice
Published in Journal of Toxicology and Environmental Health, Part A, 2022
Lei Wang, Maya Rajavel, Ching-Wen Wu, Chuanzhen Zhang, Morgan Poindexter, Ciara Fulgar, Tiffany Mar, Jasmine Singh, Jaspreet K. Dhillon, Jingjing Zhang, Yinyu Yuan, Radek Abarca, Wei Li, Kent E. Pinkerton
Infiltration of immune cells in bronchoalveolar lavage fluid (BALF), inflammation of lung tissue (histopathology), distribution of CD4-, CD8-, and CD25-positive T cell markers in lung tissue, and expression of interferon mRNA (IFN) in spleen tissue were determined following IAV inoculation. T cells are the most important lymphocyte trafficking to the lungs during the first week of viral infection. The CD4, CD8, and CD25 T cell markers were selected to visualize populations of helper, cytotoxic, and regulatory T cells, respectively. CD4-positive, helper, T cells interact with antigen-presenting cells (e.g., macrophages) to shape pathogen-specific, adaptive immune responses, such as antibody production and cytotoxic T cell activation (Figure 1; Sant et al. 2018a; Sant, Richards, and Nayak 2018b; Lee and Lawrence 2018). CD8-positive, cytotoxic, T cells induce death of pathogen-infected, damaged, or dysfunctional cells (Pizzolla et al. 2017; Smed-Sörensen et al. 2012). CD25-positive, regulatory T cells are a subset of CD4-positive cells which suppress the activities of other T cells, B cells, and antigen-presenting cells (Corthay 2009). These three cell types are important factors in the immune response to viral infections (Rosendahl Huber et al. 2014).
A mathematical model of cytotoxic and helper T cell interactions in a tumour microenvironment
Published in Letters in Biomathematics, 2018
Heidi Dritschel, Sarah L. Waters, Andreas Roller, Helen M. Byrne
There are two populations of T cells, helper and cytotoxic, which are distinguished by their expression of CD4 and CD8 proteins, respectively. Naive helper T cells are activated by antigen presented with a major histocompatibility complex (MHC) class II molecule. (A glossary of the terminology used in this article is provided in Appendix 1.) Naive cytotoxic T cells are activated by antigen presented with an MHC class I molecule. Once activated the helper and cytotoxic T cells perform complementary functions to eliminate the tumour. Helper T cells further differentiate into subpopulations classified by the specific cytokines that they produce. In this way, they regulate multiple aspects of an immune response. For example, they promote the proliferation of cytotoxic T cells, they recruit and promote cells of the innate immune response, and they control levels of inflammation at the tumour site (Hung et al., 1998; Magombedze et al., 2013). (In this work, we do not distinguish these subpopulations.) Cytotoxic T cells scan the body for transformed cells (cancer cells) to which they bind before inducing cell killing.
Effect of low dose radiation from general X-ray to T-cell lymphocyte expression using an in vitro method
Published in Radiation Effects and Defects in Solids, 2022
Gunjanaporn Tochaikul, Nuttapong Danthanavat, Chalermchai Pilapong, Nutthapong Moonkum
T cells are an essential part of the immune system (18). The CD4+ T helper cells (Th cells), play an important role in the immune system, particularly in the adaptive immune system (19). CD8+ T cells (often called cytotoxic T lymphocytes, or CTLs) are very important for an immune defence against intracellular pathogens, including viruses and bacteria, and tumour surveillance (20). Typically, The CD4/CD8 ratio in the peripheral blood of healthy adults and mice is about 2:1, and an altered ratio can indicate diseases related to immunodeficiency or autoimmunity (21).