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Cellular and Molecular Basis of Human Biology
Published in Lawrence S. Chan, William C. Tang, Engineering-Medicine, 2019
T-lymphocytes. T-lymphocytes or T-cells, with a cell surface marker of CD3, are responsible for adaptive immune response. Possessed on the surface a T cell receptor (TCR) that can interact with MHC molecules on the surface of APCs, T cells are instrumental for long-term memory of immune defense, such as in the case of vaccine-initiated immune defense. The recent development of utilizing molecularly engineered T-cells for immunotherapy against cancer truly illustrates the important role of T cells in the health affairs of humans (Butler and Hirano 2014, Perica et al. 2014). Two major T cell types are important for human immune defense, the CD4+ helper T cells and the CD8+ cytotoxic T cells. More details on T-cells’ role in human medicine are discussed in Precision Chapter (Chapter 12).
Exopolysaccharides of Halophilic Microorganisms: An Overview
Published in Devarajan Thangadurai, Jeyabalan Sangeetha, Industrial Biotechnology, 2017
Pradnya P. Kanekar, Siddharth V. Deshmukh, Sagar P. Kanekar, Prashant K. Dhakephalkar, Prabhakar K. Ranjekar
Satpute et al. (2010) have reviewed work on EPS of marine microorganisms, for example, Bacillus, Halomonas, Planococcus, Enterobacter, Alteromonas and cyanobacteria. Halomonas eurihalina strain F2–7 was found to produce large amounts of polyanionic EPS. The polymer is a potent emulsifier and shows pseudoplastic behavior. The EPS F2–7 may have a range of applications in pharmaceuticals, food industry and biodegradation (Quesada et al., 1993; Calvo et al., 1995; Bejar et al., 1998). The polymer also has immunomodulatory activity in vitro. It enhances the proliferative effect of human lymphocytes as a response to the presence of anti-CD3 monoclonal antibody in blood (Perez-Fernandez et al., 2000). EPS produced by Halomonas ventosae and Halomonas anticariensis were found to form solutions of low viscosity and have pseudoplastic behavior (Mata et al., 2006). They also have capacity to bind with cations suggesting their applications in bioremediation. Carmen et al. (2008) isolated moderately halophilic bacteria from saline soils in Spain. The organisms were designated as Halomonas cerina sp. nov. and found to produce EPS. Poli et al. (2007) have reported Halomonas alkaliantarctica strain CRSS from Salt lake in Cape Russell in Antarctica which produces EPS having high viscosity and different chemical composition on various substrates utilized as nutrients.
Host Response to Biomaterials
Published in Claudio Migliaresi, Antonella Motta, Scaffolds for Tissue Engineering, 2014
Sangeetha Srinivasan, Julia E. Babensee
A T-cell, on an average, expresses about 30,000 T-cell receptors (TCRs) on its surface.108 Antigen recognition by most T-cells is mediated through the TCR. A TCR is composed of two chains, TCR-a and TCR-b, bridged by a disulfide bond. The ^-terminal variable region shares homology with immunoglobulin V, including a constant region similar to immunoglobulin C domains and a hinge region with a disulfide bond.95 It also has a hydrophobic transmembrane domain and a short C terminal cytoplasmic tail. TCR couples with CD3 complex on the T-cell surface to function as a single unit. CD3 consists of three constant chains and one homodimeric Z chain that has a very short extracellular domain. CD3 molecules possess a negative charge that aids in the formation of the complex since the
Effects of long-term high-level lead exposure on the immune function of workers
Published in Archives of Environmental & Occupational Health, 2022
Jianrui Dou, Le Zhou, Yi Zhao, Wu Jin, Huanxi Shen, Feng Zhang
The main cells involved in immune responses are T-lymphocytes, B-lymphocytes, monocytes/macrophages, natural killer cells, and leukocytes. T-lymphocytes account for approximately 70% of peripheral blood lymphocytes, being important participants of host immune responses and primarily reflecting cellular immune function. CD3 is a surface marker of mature T-cells and can reflect the total number of T-cells in vivo. T-lymphocytes can be divided into helper T-lymphocytes with the CD4 surface marker, suppressor T-lymphocytes with the CD8 surface marker, regulator/suppressor T-lymphocytes, and memory T-lymphocytes. Among these subtypes, the ratio between CD4+/CD8+ cells is an important indicator that reflects the stability of the immune system. If this ratio decreases, it indicates that the overall immune function of the host has decreased. One study in Portugal illustrated that even if blood Pb did not reach the maximum legal limit of 70 µg/dL, the percentage of CD8+ cells in exposed individuals was significantly lower than in the control group, and the CD4+/CD8+ cells ratio was significantly increased.8 Other studies showed that the percentages of CD3+ and CD4+ cells and the CD4+/CD8+ ratio were significantly decreased in some workers exposed to Pb, while the percentage of CD4+ cells negatively correlated with blood Pb levels and exposure time, and the percentage of CD8+ cells increased significantly.9,10 Wu and colleagues11 detected CD3 gene expression levels in peripheral blood mononuclear cells of 46 patients of Pb poisoning (11 cases in an observation group and 35 cases in a mild Pb poisoning group). The median expression levels of the CD3γ and CD3ε genes in the observation and mild Pb poisoning groups (6.89% and 5.87%) were higher than those in the control group (p < .05); CD3ζ and CD3ε positively correlated with the seniority of Pb poisoning patients. Liu et al.12 also found increased expression of the CD3 gene in the peripheral blood of workers exposed to Pb (p < .05). Our results in the current study were consistent with these findings as the levels of CD3 in the serum of the high-Pb group were higher than those in the low-Pb group. The level of CD3 positively correlated with blood Pb concentration (Rs = 0.378, p = .007). However, there was no significant difference between the two groups in helper/inducer T-cells (CD3+CD4+), suppressor/cytotoxic T-cells (CD3+CD8+), or the CD4+/CD8+ ratio. This indicated that the cellular immune response of a host may be improved under high-Pb concentrations. The activation of T-cells following Pb poisoning is intense; however, due to long-term exposure to high levels of this metal, tolerance or fatigue of the immune response possibly could develop and the antagonism between T-lymphocyte subsets could reach a balance. There is no statistical difference in the percentage values for the immune cells and the cellular immune response is in a relatively stable state, which needs to be further studied.