General Thermography
James Stewart Campbell, M. Nathaniel Mead in Human Medical Thermography, 2023
The thymus gland is located in the anterior chest, in front of the upper portion of the heart and trachea (Figure 10.61). It is proportionally large in infancy but shrinks with age. At puberty, it weighs 30 to 50 grams, and by old age, it typically weighs 5 to 15 grams. The thymus rarely becomes neoplastic, developing into a lymphoma or thymoma. Lymphomas occupying superficial lymph nodes may appear warm on thermographic analysis, but this warmth is not associated with the thymus gland itself.165 Thymomas, on the other hand, may become large enough to become detectable as a warm area in the upper anterior chest, but no studies confirming this have been published. Though some thermographers claim that cool areas over the anterior or posterior upper chest are a sign of “underactive thymus,” this is doubtful because of the small size and normally low metabolic activity of the gland in adulthood. A cool area over the upper sternum may instead be due to the presence of thymic cysts, which may become as large as 4 cm (1.6 in.) in diameter. No studies are available concerning cool areas over the thymus gland. MRI and CAT scans can determine anatomic thymus abnormalities, while hematology can monitor the physiologic and pathologic activity of the gland.166
The Aging Immune System
Constantin A. Bona, Francisco A. Bonilla in Textbook of Immunology, 2019
One of the earliest known and most consistent changes in the immune system with aging is the involution of the thymus. This process begins at puberty and continues through middle age. The mass of the thymic stroma, as well as resident lymphocytes, gradually decreases and the organ is replaced by a small fibrotic remnant of about 10% of its original size. The thymus has a fundamental role in T cell development (see Chapter 6). Loss of the thymus in infancy or childhood may be associated with immune deficiency. Although T cell development continues (at a slower pace) in the adult thymus, its loss later in life is generally well-tolerated. Presumably, a sufficient population of long-lived T cells has developed before involution begins. The number of immature T cells in the peripheral circulation increases with age, reflecting the impairment of the thymic maturational environment. With involution, levels of thymic hormones slowly fall, and are undetectable by age 50–60. Exogenous thymic hormones may improve T cell function in aged individuals.
The Great Influenza
Rae-Ellen W. Kavey, Allison B. Kavey in Viral Pandemics, 2020
Cytokines are central to the induction of the body’s immune response to viral infection via activation of specialized white cells including natural killer (NK) cells, white cells which are part of the innate immune system, mediating the initial response to infection by responding quickly to detect and kill virally infected cells. The innate immune system attempts to limit a viral infection immediately, before the adaptive antigen-specific immune response is engaged. The antigen-specific response to infection is mediated by T cells (thymus cells) and B cells (bone marrow- or bursa-derived cells), the major cellular components of the adaptive immune response. T cells are responsible for cellular immunity, a protective immune response that involves activation of phagocytic white cells and the release of cytokines and chemokines in response to a viral invader. B cells proliferate and secrete large amounts of virus-specific antibodies. These antibodies bind to the surface of the viral antigen which is then identified for elimination. Once virus-specific antibodies are created, they persist and will bind to the surface whenever that specific virus is re-introduced, preventing future infection.7,8
Effects of pre and postnatal 2450 MHz continuous wave (CW) radiofrequency radiation on thymus: Four generation exposure
Published in Electromagnetic Biology and Medicine, 2022
Fazile Cantürk Tan, Betül Yalçin, Arzu Hanım Yay, Burak Tan, Korkut Yeğin, Süleyman Daşdağ
The thymus is a central organ of the immune system and the lymphatic system, which differentiate into antigen-recognizing cells and lymphocytes produced by the bone marrow in mammalian cells (Dominguez-Gerpe and Rey-Menéndez 2003; Miller 2020; Rezzani et al. 2014). During early embryogenesis, with the onset of hematopoiesis begins development of the immune system and then throughout prenatal life continues with successive hematopoietic cell production, cell migration, and differentiation (Laudisi et al. 2012). The thymus is vulnerable to physiological alters such as pregnancy, aging, and external factors. In recent decades, researchers have found that ionizing and non-ionizing radiation achieve an external stimulus that changes thymus functions and modulates immune responses (Chen et al. 2000; Hekmat et al. 2013; Quaglino et al. 2004).
Immune memory limits human longevity: the role of memory СD4+ T cells in age-related immune abnormalities
Published in Expert Review of Vaccines, 2020
Victor Ivanovich Seledtsov, Alexei A. von Delwig
As alluded to above, subject to thymus selection and subsequent differentiation in the periphery, naïve T cells are formed to effectively respond to antigenic stimulations. Upon infection or vaccination, antigenic peptides released in the course of antigen processing bind to self-MHC molecules on the surface of antigen-presenting cells (APCs) for subsequent recognition by TCR. The ensuing TCR signals cooperate with other signals of cytokine, co-stimulatory, chemokine, integrin, and metabolic origin to generate both effector and memory T cells of different phenotypes [5,6]. In contrast to TCR, B-cell receptors (BCR) recognize intact Ags independently of Ag processing and MHC molecule-dependent antigen presentation. However, both B-cell differentiation and generation of memory B cells require continuous co-stimulatory molecule-dependent and cytokine-dependent help provided by Ag-reactive helper T cells [3].
Proteome of thymus and spleen reveals that 10-hydroxydec-2-enoic acid could enhance immunity in mice
Published in Expert Opinion on Therapeutic Targets, 2020
Pei Fan, Bin Han, Han Hu, Qiaohong Wei, Xufeng Zhang, Lifeng Meng, Jing Nie, Xiaofeng Tang, Xinyue Tian, Lu Zhang, Liping Wang, Jianke Li
As an immuno-organ, the thymus is responsible for generating and accommodating T cells that engage in immune responses [20]. T cell precursors originate from bone marrow, and migrate to the thymus for maturation [39]. When exposed to CP, T cell proliferation and myeloid cell differentiation could be inhibited, thereby triggering immuno-suppression by lessening T cells in the thymus. T cell proliferation is regulated by multiple cytokines, such as interleukin-4, a potent T cell growth factor [40]. This is also supported by the finding that the GO term of response to interleukin-4 in the thymus is inhibited via CP induction that causes T cell developmental retardation. Mature T cells require being positively and negatively selected in the thymic cortex and medulla, respectively, through complicated and stepwise manners to gain competence in immune response [41]. Cytotoxic T cells, a major T cell type, can directly target and wipe out infected cells within the body [42,43]. Here, pathways of the negative T cell selection and the positive regulation of leukocyte mediated cytotoxicity were attenuated by CP. Interestingly, these T cell involved functions in the thymus were found to be revived by supplementation with 10-HDA in the CP injected mice. This evidence suggests that 10-HDA may be a key role player for T cell proliferation, activation, and cytotoxicity in regaining the thymus weight.
Related Knowledge Centers
- Adaptive Immune System
- Epithelium
- Major Histocompatibility Complex
- Thymocyte
- Sternum
- Immune System
- Lymphocyte
- Heart
- T Cell
- Thymic Involution