Explore chapters and articles related to this topic
Lymphocytes and The Immune Response
Published in Richard C. Niemtzow, Transmembrane Potentials and Characteristics of Immune and Tumor Cell, 2020
Lymphocytes evolving within the thymus acquire the functions and surface antigens of the T cell population. The epithelial cells of the thymus secrete hormone-like factors which play a role in T cell maturation. Thymic factors, such as thymosin and thymopoietin have been proposed as T cell maturation factors. The maturation events occur initially in the thymic cortex, where large numbers of rapidly dividing cells are found. Many of these cells subsequently die within the cortex. The small lymphocytes remaining have already acquired T cell specific surface antigens. There is a gradual migration to the thymic medulla, where further maturation occurs. The resulting T cells then leave the thymus for the peripheral lymphoid organs and/or circulation in the blood and lymph. These T cells have important immunoregulatory functions and are responsible for the various phenomena of cell-mediated immunity (CMI). CMI plays a primary role in host resistance to viral, bacterial, fungal, and parasitic invasions, tissue grafts, and neoplasia. The thymus begins to involute when humans reach puberty, with atrophy beginning in the cortex.
T Cells:Regulation and Cellular Immunity
Published in Constantin A. Bona, Francisco A. Bonilla, Textbook of Immunology, 2019
Constantin A. Bona, Francisco A. Bonilla
Thymopoietin is a 5.5 kDa protein with several biological activities. It induces T cell differentiation, and enhances the activity of mature T cells. It also interacts with acetylcholine receptors, and stimulates release of adrenocorticotrophic hormone and β-endorphin by the pituitary. A highly homologous protein known as thysplenin differs at only four amino acids, but has distinct biological activity; it induces both B and T cell differentiation. The thymosins are a group of low molecular weight (3–4 kDa) proteins which are also active in various aspects of thymic T cell differentiation. The precise roles of these molecules in lymphocyte differentiation still require much clarification. Another factor, interleukin-7 (see Chapter 7) is also produced by thymic epithelial cells, and promotes cell division of immature thymocytes.
The Thymus in the Regulation and Control of Cell Growth
Published in Nate F. Cardarelli, The Thymus in Health and Senescence, 2019
The only function of Tdt appears to be the adding of deoxyribonucleotides to the end of DNA primers, although Baltimore suggests that it also acts as a somatic mutagen.569 Pazmino and Ihle also suggested that Tdt is an intrinsic somatic mutagen involved in the differentiation of T cells.570 Thymic Tdt activity appears to reside in the cortical thymocytes,571,572 and decreases with adult age.570 It varies in concentration with cancerous states and can be used to distinguish human acute lymphoid leukemia from myeloid leukemia.573 Silverstone et al. note that thymopoietin, a thymic hormone induces the development of bone marrow T cell precursors.568 This research group suggests that Tdt synthesis is the earliest known property of cells that undergo thymusdependent development. Furthermore, Tdt disappears prior to the final maturation of the T cell. The later work of Brown is confirming.574 He found that Tdt is a marker for lymphoid cells, and most remarkedly it shows up in 2-day-old frog embryos well before the appearance of the thymus!
Preformulation studies of thymopentin: analytical method development, physicochemical properties, kinetic degradation investigations and formulation perspective
Published in Drug Development and Industrial Pharmacy, 2021
Mengyang Liu, Darren Svirskis, Thomas Proft, Jacelyn Mei San Loh, Jingyuan Wen
Thymopentin (TP5) has recently garnered much interest due to its immunomodulatory activities and potential to treat human and animal immunological diseases [1,2]. TP5 is a small therapeutic pentapeptide (Arg-Lys-Asp-Val-Tyr, molecular weight 679 g/mol), which is the active component of the larger protein thymopoietin II, comprised of 49 amino acids [3]. As an immunomodulatory agent, it has been widely used in the treatment of cutaneous T-cell lymphoma, cancer, immunodeficiency, rheumatoid arthritis, acquired immunodeficiency syndrome (AIDS) and severe acute respiratory syndrome (SARS) [4]. The exact mechanism of action on the immune system is currently unclear, although attempts have been made to explain its immunoregulatory effects [5]. The dominant mechanism of TP5 may be the upregulation of mRNA expression of interleukin 2 or 22 and their signaling pathways, which include: (1) control of local inflammation by promoting CD4+ T cell differentiation into peripherally induced regulatory T cells and related T helper cells; (2) control of autoantibody production by reducing T cell differentiation into T helper 17 cells and T follicular helper cells; and (3) control of T cell mediated autoimmunity by producing effector memory CD8+ T cells with interleukin 2 signal strength [5].
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].