Systems IntegrationPsychoneuroimmunology
Len Wisneski in The Scientific Basis of Integrative Health, 2017
Thymic hormones regulate IL-2 production, which then aids in the maturation of thymocytes and the presence of IL-2 receptors on mature T cells. This effect appears to be synergistic with IL-1 (Hadden et al., 1991). In addition, numerous hormones produced within the thymus are classically thought of as pituitary hormones (e.g., GH, prolactin, ACTH, luteinizing hormone [LH], and others). I cannot emphasize enough the importance of such findings. It has forced us to alter our whole concept of how the body functions. These thymic hormones have paracrine–autocrine actions, which serve to regulate immune action and influence neuroendocrine functions that affect the regulation of the HPA axis (Savino et al., 1998). Glucocorticoids play a particularly interesting role in T-lymphocyte development. At high concentrations, they induce thymocyte apoptosis, but at lower concentrations, they actually potentiate thymocyte maturation (Vacchio et al., 1998). We will come back to this point when we look at the role that glucocorticoids play in stress (see Chapter 3, which covers the stress system).
Thymus Influence on Differentiation and Functional Maturation of T Lymphocytes
Marek P. Dabrowski, Barbara K. Dabrowska-Bernstein in Immunoregulatory Role of Thymus, 2019
Perhaps the most spectacular goal achieved with the aid of experimental thymectomy relates to endocrine function of the thymus, the dramatic effects of neonatal thymectomy reverted by the implantation of milipore chamber with the thymus inside15 added new value to earlier observations of lymphocytopoietic abilities of different thymic extracts.16-18 In consequence, thymectomized animals were experimentally treated with thymic cell-free extracts whereby the restoration and/or modification of immune functions was reported. These early reports relate to the increased survival of neonatally thymectomized mice,19 the restoration of graft-vs.-host reactivity20 and the recovery of homograft response.21 Gradually, it has become clear that the thymus developes hormone-like activity mainly responsible for T cell maturation. Moreover, thymectomy experiments have shown that putative thymic hormones may, to some extent, replace the thymus function driving T cell development in peripheral lymphoid tissues. Nonetheless, thymectomy could hardly be expected to provide information on the exact nature of the thymic driven T cell differentiation. For obvious reason, no insight into the internal thymic microenvironment has been offered in substitutive experiments, and so, the thymus itself has become again a focus of interest.
Immune system of the newborn
Prem Puri in Newborn Surgery, 2017
Lymphocyte development occurs along two distinct pathways leading to the production of the two major lymphocyte populations, T-cells and B-cells, which have very different biological effector functions. The thymus is the site of development of T-cells, which are responsible for the range of effector functions collectively termed cell-mediated immunity. Cell-mediated immunity ranges from the release of soluble factors such as cytokines, which regulate the activity of all cells of the immune system, to direct cytopathic effect of cytotoxic lymphocytes on viruses or tumor cells. B-lymphocytes, on the other hand, have a more restricted effector function, confined to the synthesis and secretion of humoral antibodies in each of the immunoglobulin classes, IgG, A, M, D, and E. More recently, B-lymphocytes have been shown to be capable of presenting antigen to T-cells.72 In man, the site of synthesis of B-lymphocytes is the bone marrow.
Growth hormone enhances the CD34+ stem cells repopulation of the male albino rat thymus gland in cyclophosphamide induced injury: immunohistochemical and electron microscopic study
Published in Ultrastructural Pathology, 2023
Amira I. Shrief, Walaa H.E. Hamed, Shireen A Mazroa, Amal M. Moustafa
Examination of the sections in the thymus gland of all subgroups of control rats (group І) revealed the same structure. The thymus gland was covered with a thin connective tissue capsule and was subdivided into intercommunicating lobules by thin connective tissue septa. Each lobule was divided into outer darkly stained cortex and inner pale medulla with a clear demarcation between them (Figure 1a). The thymic cortex was populated mainly by large number of closely packed thymoblasts and fewer epithelial reticular cells (ERCs). Thymoblasts had large rounded nuclei. The ERCs had oval to round pale stained nuclei. Macrophages and blood capillaries were also seen (Figure 1b). The thymic medulla was formed of loosely packed thymocytes with small rounded deeply stained nuclei, more prominent ERCs and few Hassall’s corpuscles. Hassall’s corpuscles were formed of a central hyaline acidophilic mass surrounded with one layer of ERCs (Figure 1c).
The use of immunotherapy for the treatment of tuberculosis
Published in Expert Review of Respiratory Medicine, 2018
Octavio Ramos-Espinosa, León Islas-Weinstein, Marco Polo Peralta-Álvarez, Manuel Othoniel López-Torres, Rogelio Hernández-Pando
Hormones isolated from the thymus, such as thymopoietin, have been modified in order to obtain immunostimulant factors. This is the case of thymopentin, a synthetic pentapeptide with immunoregulatory activity (TP-5, RKDVY) constituted by six arginine residues (RR-6, RRRRRR) at the N and C terminal to obtain the cationic peptides, RR-11 (RKDVYRRRRRR-NH2) and RY-11 (RRRRRRRKDVY-NH2) [116]. BALB/c mice were used in a multiresistant Mtb infection model. Assessment of the individual thymopentin therapy and in combination with moxifloxacin was performed to measure their impact on the bacillary load in spleen and lungs. Additionally, T lymphocytes subsets and PD-1 expression levels were determined in peripheral blood. A decrease in the bacillary loads in lungs and spleen of mice treated with thymopentin was observed. A synergistic effect with moxifloxacin achieved a greater decrease in bacillary loads than the individually treated groups. Th1 and Th17 cells in peripheral blood of treated mice with thymopentin were higher than those of the control group. Th2 and Treg responses were low in the thymopentin-treated group, with a decreased expression of PD-1 in T and B lymphocytes as well as monocytes in peripheral blood of individuals treated with thymopentin in comparison to the control group [117].
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