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The Scientific Basis of Medicine
Published in John S. Axford, Chris A. O'Callaghan, Medicine for Finals and Beyond, 2023
Chris O'Callaghan, Rachel Allen
B and T lymphocytes equip the adaptive immune response with its specificity, diversity and memory. The initial activation of naive T cells requires recognition of antigen by the T-cell receptor (TCR) and sufficient co-stimulatory signalling and appropriate cytokines. Co-stimulation is regulated by proteins which serve as immune checkpoints to restrain the activation of adaptive immunity. Successful activation of naive T cells leads to the proliferation of a population of effector cells which, in the case of helper T cells (THcells), support the functions of B cells and cytotoxic T cells (CTLs).
Infection and Inflammation
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Erik H. J. G. Aarntzen, Andor W. J. M. Glaudemans
Lymphocytes: Multiple in vitro studies have shown increased glucose metabolism in different stages of functional differentiation of T cells [61]. When a naïve T cell encounters its cognate antigen in the proper stimulatory context, it undergoes a transcriptional program that is characterized by proliferation, rapid growth, and induction of specialized effector functions belonging to effector T cells. This reprogramming requires metabolic adaption from a catabolic metabolism to an anabolic metabolism because, unlike quiescent states, nutrients will not be used for homeostasis but will be incorporated in biosynthetic precursors required for daughter cells and effector functions. This demand for biosynthetic precursors drives effector T cells to increase their glycolysis, even in the presence of sufficient levels of oxygen. To the contrary, T cells destined to become memory cells must maintain catabolic metabolism, underlying their longevity and may postpone their terminal differentiation, so they rely mainly on mitochondrial fatty acid oxidation.
T Cells:Regulation and Cellular Immunity
Published in Constantin A. Bona, Francisco A. Bonilla, Textbook of Immunology, 2019
Constantin A. Bona, Francisco A. Bonilla
Memory T cells have distinct surface markers and a different profile of cytokine secretion reflecting their unique pattern of activation and role in immune responses (Table 6–VIII). The major distinguishing surface marker of memory T cells is CD45 (see above). Naive T cells express the CD45RA isoform, while activated and memory T cells express CD45RO. Memory cells also express increased amounts of adhesion molecules such as LFA-1 (CD11a/CD18), and CD2 and CD58. Furthermore, on naive cells, several of the co–stimulatory molecules are separate from the TCR, and they must become closely associated with it for activation to proceed. On the memory cell, surface CD4 and CD45RO are already in close proximity to the TCR complex. These alterations of surface phenotype render the memory cell more receptive to stimulation in some situations. For example, both naive and memory cells respond vigorously when antigen is presented by dendritic cells or by activated B cells. Naive cells respond poorly when antigen is presented by resting B cells or macrophages, while memory cells are easily stimulated by these populations.
Clinical significance of serum glucose to lymphocyte ratio as a prognostic marker in peritoneal dialysis patients
Published in Renal Failure, 2023
Jiexin Chen, Ruiying Tang, Xiaojiang Zhan, Jihong Deng, Yanxia Zhang, Haibo Long, Fenfen Peng, Na Tian, Yueqiang Wen, Xiaoyang Wang, Xiaoran Feng, Ning Su, Xingming Tang, Xianfeng Wu, Qian Zhou, Qingdong Xu
PD patients show unbalanced lymphocyte metabolism, which is normally tightly regulation by the immune response to glycolysis [19,20], and the expansion and function of T cells may be repressed under high glucose conditions. Malnutrition, accumulation of uremic toxins, and inflammation may lead to the inability to gain adequate nutrients, thereby accelerating the aging process of premature T cells, and causing significant barriers to T cell function in patients with PD [21]. Naïve T cells play a key role in the maintenance of adaptive immunity. Alterations in T cell subsets may attenuate the response to antigens and increase the risk of CVD in patients with kidney failure [22]. CVD mortality is influenced by a variety of factors, including smoking status, blood pressure, cholesterol, and overweight [23,24], while the importance of hyperglycemia and abnormal lymphocyte metabolism should not be ignored.
Survivin as a biological biomarker for diagnosis and therapy
Published in Expert Opinion on Biological Therapy, 2021
Yuming Li, Wenshu Lu, Jiarun Yang, Mark Edwards, Shisong Jiang
DCs are the most important antigen-presenting cells (APC) in the mammalian immune system. For the most part, DCs exist in an immature state, both in the circulation or resident in tissue. They only mature and become activated after phagocytosis and processing of antigens. DCs exhibit high expression of the MHC molecules which present processed antigens to T cells in the form of an antigen-MHC complex. This complex can activate naïve T cells through antigen-specific engagement with the T cell receptor. Activated T cells then differentiate to become specific CD4+ T helper cells or specific CD8+ cytotoxic T cells (CTL) that suppress infection or tumor growth. The significance of this pathway is reflected in the fact that over 60% of immunotherapy clinical trials using SVN have focused on a DC strategy to stimulate strong and specific anti-tumor T cell responses (Table 1).
Eat clean and safe food: a food-based dietary guideline for the elderly in South Africa
Published in South African Journal of Clinical Nutrition, 2021
Makenzie Miller, Wilna Oldewage-Theron, Carin Napier
The gradual accumulation of molecular and cellular damage that occurs during the ageing process leads to a general decrease in physiological reserves. These changes are largely unavoidable and vary widely among individuals, even those of the same age.14 As individuals age, their immune function is reduced due to a decline in both mucosal immune function and adaptive immune function. Low levels of stomach acid and decreased intestinal motility (as a result of the natural ageing process or medication side effects) reduce older adults’ ability to fight off infection in the gastrointestinal tract (GIT). Loss of adaptive immune function reduces individuals’ response to new pathogens, such as those present in contaminated foods.7 As ageing occurs, the immune system shifts from utilising naive T-cells (those which have never been exposed to an antigen) to the predominant use of memory T-cells. The reduction in naive T-cells leads to a decreased ability to respond to new antigens, such as those present in newly encountered diseases, mutated disease agents, and those in vaccines. A decrease in naive T-cell levels further leads to failure of Interleukin-2 (IL-2) gene transcription, resulting in lowered T-cell responses in elderly individuals. Reduction in T-cell and B-cell efficiency causes lowered immune response among the elderly population.4