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Basic Chemical Hazards to Human Health and Safety — II
Published in Jack Daugherty, Assessment of Chemical Exposures, 2020
The lymphocytes that produce cellular immunity are called T-cells, which attack only those antigens that have been processed by other cells. Phagocytes engulf antigens and break them down. The cell fragments and proteins from the infection agent are displayed on the surface of the phagocyte, bound by cell surface proteins called human leukocyte antigen proteins, produced by genes called the major histocompatibility complex, which are unique markers that identify self from nonself. T-cells respond to the HLA protein and foreign antigen combination in a molecular lever lock and key fashion. Killer T-cells secrete a cytotoxic substance to destroy antigens. Memory T-cells are dormant until the same antigen reappears, then they attack swiftly. Helper T-cells promote T-cell activation, stimulate phagocytic activity, and enhance the humoral immunity process. Suppressor T-cells produce delayed inhibition of cellular and humoric responses.
Putting a Cell Together
Published in Thomas M. Nordlund, Peter M. Hoffmann, Quantitative Understanding of Biosystems, 2019
Thomas M. Nordlund, Peter M. Hoffmann
T cells are white blood cells (lymphocytes) that play a central role in immunity. (“T” stands for thymus, where the T cells grow.) They are characterized by a special receptor on their cell surface called T cell receptors (TCRs) that interact with the major histocompatibility complex (MHC, a protein) on an antigen presenting cell (APC) that has managed to “bite off” a fragment of a foreign cell’s (or virus’s) protein or glycoprotein called an antigen (Figure 7.16). “Professional” APCs are cells that specialize in obtaining an antigen from an invading cell or virus and then displaying a fragment of the antigen, bound to an MHC molecule, on their membrane. The T cell recognizes and interacts with the MHC molecule complex on the membrane of the APC. (Note so far the T cell is not dealing directly with the invading cell.) When the T cell binds to the APC, the latter gives an additional signal that activates the T cell. The T cell then secretes a chemical (cytokine) that causes growth of more T cells, some of which become capable of killing the invading cell or cell that has been infected with virus. Huge amounts of biochemical and genetic information are known about the many components of this type of immune response, but we will focus on what takes place structurally when the T cell binds the MHC. For a more complete description of the immune recognition response, see K. Singleton et al.16 Read the Journal of Immunology for continuing, up-to-date coverage of discoveries about the immune response.
Bayesian Nonparametric Mixture Models
Published in Sylvia Frühwirth-Schnatter, Gilles Celeux, Christian P. Robert, Handbook of Mixture Analysis, 2019
Example 6.2 (T-cell receptors)Guindani et al. (2014) consider data on counts of distinct T-cell receptors. The diversity of T-cell receptor types is an important characteristic of the immune system. A common summary of the diversity is the clonal-size distribution. The clonal-size distribution is the table of frequencies Fy^ of counts y = 1, 2, …, n. For example, F2^ = 11 means that there were 11 distinct T-cell receptors that were observed twice, etc. Table 6.1 shows the observed frequencies for one of the experiments considered in Guindani et al. (2014).
Modelling the dynamics of virus infection and immune response in space and time
Published in International Journal of Parallel, Emergent and Distributed Systems, 2019
G. Bocharov, A. Meyerhans, N. Bessonov, S. Trofimchuk, V. Volpert
A central problem of infectious disease pathogenesis is related to the mechanisms of T cell exhaustion, associated with various outcomes of infections. Mathematical models assist in revealing a mechanistic view of the infection course and outcomes [12,13]. In contrast to previous studies of exhaustion, we have shown that in chronic infections the dynamics of virus and immune cells in space and time can be a continuum of different regimes ranging from steady states with a complete or a partial elimination of immune cells on one side to non-monotone dynamics in the form of travelling waves and irregular oscillations on the other side. The time-delays reflecting the clonal expansion of cells and the programming for apoptosis appear to be key control parameters. The mapping of the parameter space on the patterns of spatio-temporal dynamics being a subject of our study can further assist via a multi-disciplinary approach in solving a fundamental problem of optimising the efficacy of anti-T cell exhaustion therapies in chronic virus infections [35–37].
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
T cells are one of the most important components of the immune system in the fight against cancer. They originate from pluripotent haematopoietic stem cells in the bone marrow which migrate to the thymus where they mature into naive T cells. The naive T cells move to the lymph nodes where they become activated on contact with their cognate antigens. Activated T cells proliferate rapidly to produce a substantial army of antigen-specific T cells. These short lived T cells are then transported through the blood vessels to the tumour where they bind to and kill infected cells and also produce cytokines that recruit other immune cells to the tumour. This process continues until either the tumour has been removed or the tumour adapts to, and evades, targetting by the T cells (Chen and Mellman, 2013; Janeway et al., 2001).
Genetic variants affecting chemical mediated skin immunotoxicity
Published in Journal of Toxicology and Environmental Health, Part B, 2022
Isisdoris Rodrigues de Souza, Patrícia Savio de Araujo-Souza, Daniela Morais Leme
Langerhans cells (LC) are professional APCs of the epidermis that migrate to lymph nodes and stimulate T lymphocyte responses (Clayton et al. 2017; Quaresma 2019). As a dendritic cell (DC), LC might capture, process, and present antigens to naïve T cells (Klechevsky 2015). During skin sensitization, LC mobilization towards the regional lymph nodes and concomitant maturation (to DCs) are induced and regulated by cutaneous cytokines. Thus, LC process and present the captured antigen on their surface associated with MHC molecules. This complex may be subsequently recognized by naïve T cells, thus instigating clonal expansion of antigen‐specific T lymphocytes and enabling development of cellular immunological memory (Divkovic et al. 2005).