Cells At Work Helper T Cell

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At some point in biology class, we’ve heard about these T cells that play an important role in the immune system. But what are the exact connections and what exactly do T cells do?

What are the T cells?

T cells are an important component of the acquired immune system in the blood. They form a subgroup of white blood cells called leukocytes. They come in different subgroups:

  • Granulocytes
  • Monocytes (precursor of macrophages)
  • Lymphocytes

The latter are in turn subdivided into B lymphocytes (B cells) and T lymphocytes (T cells). While B cells are central to the humoral immune response, T cells play an important role in the cellular immune response as well as in the coordination of the various immune responses. The cellular immune response is responsible for rendering diseased cells harmless. Before a T cell can perform its task, it must first be activated to recognize diseased body cells. In doing so, the T cell learns from other defense cells, such as macrophages or dendritic cells. Through this exchange, the T cells receive information about so-called antigens, i.e. recognition characteristics of unwanted invaders. Based on this information, T cells can detect diseased body cells. As part of the defense reaction, T cells take on various tasks. They are further differentiated according to their function, including the following forms:

  • T helper cells: They are responsible for ensuring that information is transferred quickly and smoothly between the various defense cells. They recognize the antigens and attract further defense cells through messenger substances. Since these cells support the immune system in various ways by exchanging important messages, they are called helper cells.
  • T-killer cells: Here the name says it all. The T-killer cells are considered the body’s own cell police and can attack diseased cells directly. They do this, for example, by emitting perforin and granzymes, specific substances that trigger the cell death of the diseased cell. T-killer cells are therefore also referred to as cytotoxic cells. The induced cell death of diseased cells prevents, for example, viruses from reproducing with the help of these cells.
  • T suppressor cells: This subgroup of T cells can suppress the immune response to an antigen in certain situations. This regulatory function prevents the immune system from reacting too violently or from mistakenly targeting healthy cells, for example. Medicine makes use of these cells in part for undesirable immune reactions, such as allergies. T suppressor cells can also be the key to preventing rejection of the supposed “foreign body” after organ transplantation.

Where are T cells and T helper cells formed?

Generally, leukocytes are formed in the bone marrow and then enter the bloodstream or migrate to the tissues. However, the T-cells make a stopover beforehand at the thymus, a gland of the lymphatic system, where they are divided into their areas of responsibility. This is where the name T cells comes from. Afterwards, the T cells are ready to serve the organism. If a pathogen appears, they quickly go into action and fight the invader. Most of the time we don’t even notice it, because a strong immune system works efficiently and purposefully. Only when the defense is weakened does the fight take longer, which becomes noticeable through fatigue or the first cold symptoms of infections.

What is the function of T-helper cells?

Every day, the immune system is exposed to a large number of pathogens such as viruses, bacteria, fungi and parasites, which it has to fight. However, in order to penetrate the body, they must first overcome various barriers and defense systems. The T-helper cells take on the task of recognizing the respective pathogen and then setting all the levers in motion so that it can be combated quickly. Once the T-helper cells have identified the invader as malignant, they secrete cytokines. These messenger substances trigger the activation of the other cells of the immune system involved – and the pathogen is already dealt a bad hand. There are several types of T helper cells that perform different tasks, but nevertheless interact with each other. Here we introduce TH1 and TH2 helper cells:

  • Type 1 T helper cells particularly support the cellular immune response, for example by interacting with macrophages, which in turn support the activation and differentiation of other T cells such as killer T cells.
  • Type 2 T helper cells on the other hand, interact predominantly with B cells and thereby initiate the release of antibodies. Thus, they interface with the humoral immune defense.

It was not until the beginning of the 21st century that another type was discovered, the type 17 T helper cells. This cell type apparently plays an important role in inflammatory processes.

How to strengthen your immune system

In order for this multitude of cells and proteins to communicate and react to each other optimally, the immune system needs your active support. After all, a weakened immune system cannot perform its demanding tasks with all its might. But you can do a few things to strengthen your body’s defenses and defy germs and pathogens – especially during the cold season:

  • The basis is a healthy diet rich in vital substances with plenty of fresh fruit and vegetables. Above all, the nutrients zinc and selenium, as well as vitamins B6 and D3, contribute to the normal function of the immune system.
  • Daily exercise and moderate sports strengthen the body’s defenses, provided you do not engage in competitive sports.
  • Fresh air and sunshine are also useful on a daily basis to keep the body’s defenses active.
  • In addition, the body needs sufficient sleep.
  • Avoid stress and ensure sufficient relaxation in everyday life.
  • Alternating showers and sauna can have a positive effect on the immune system.
  • Refrain from nicotine and alcohol, as they can significantly weaken the immune system.


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Specialty – Immunology

About one third of all blood lymphocytes are T cells (thymus-dependent lymphocytes). They can, attracted by alarm messengers, leave the bloodstream and migrate into the tissue. They return to the lymph nodes via the lymphatic pathways, from where they begin their control cycle again. Each T cell recognizes only one epitope (one T cell – one antigen) with its specific T cell receptor. T cells are divided into the following subtypes: Cytotoxic T cells (CD8+-cells) are directed at infected cells and cancer cells. For this purpose they regularly control proteins produced by body cells. For this purpose, such a cell presents small fragments of its produced proteins in a receptor, the major histocompatibility complex of class I (major histocompatibility complex, MHC I). If the cytotoxic T cell recognizes this working sample as foreign, e.g. because it is part of a viral envelope, it kills the controlled body cell and puts the immune system on heightened alert with cytokines. T helper cells (CD4+-cells) control and coordinate an immune response. They control the protein fragments presented by a macrophage in MHC II and decide whether to initiate an immune response. To do this, the activated, maturing T helper cell makes direct contact with a B or killer cell with several receptors and both cells begin to communicate with each other via cytokines. Memory T cells are deactivated but already almost fully matured T cells that are held in reserve after an infection has been overcome. They enable a rapid counter-reaction of the immune system in the event of a new infection with the pathogen in question. Memory T cells are an important part of the immunological memory formed during vaccination. Regulatory T cells (TReg, CD25+-cells), formerly called T suppressor cells, function to prevent immune reactions against endogenous tissues, maintain pregnancy, and protect beneficial intestinal bacteria from attack by the immune system (Fehervari, Z.; Sakaguchi, S. (2007): How the immune system controls itself. In: Spectrum of Science. , 54-61). They are centrally involved in optimizing an immune response and avoiding excessive reactions, thus minimizing the destruction of surrounding healthy tissue. The name T cells is derived from the thymus, the place where the T precursor cells mature and those T cells that are directed against the body’s own tissue are sorted out. The T-precursor cells are formed from lymphoid stem cells in the bone marrow. See also: B cells , natural killer cells , specific immune response.

Learning units in which the term is discussed

Autoimmunity – an introduction 30 min.

BiochemistryMedicinal chemistry and biochemistryImmunology

The immune system is a very effective defense against pathogens. However, under certain conditions it can turn against its own organism. This often results in serious autoimmune diseases such as multiple sclerosis, rheumatoid arthritis, type 1 diabetes, Crohn’s disease or celiac disease. Researchers detect “reprogramming” of immune system T-helper cells that could help fight allergies – Publication in Immunity. T-helper cells are part of the white blood cells and are the central organizing units of the immune system. Once activated, they have the special ability to evolve into vastly different, highly specialized subsets, depending on the types of pathogens they are designed to fight. For example, one subgroup, called T helper 1 cells (Th2 cells), is best suited to defend against viruses, while another, Th2 cells, specializes in fighting parasites but can also lead to the development of allergies and asthma. Five subgroups are currently known, all of which are centrally controlled by a specific gene regulator called a key transcription factor. Until now, it was assumed that the imprinting of T cells only occurs in favor of one of the five subgroups and is then irreversible. In contrast, the research group led by Lichtenberg Professor Dr. Max Löhning of the Charité – Universitätsmedizin Berlin has now been able to show that immune signals triggered by a viral infection can “reprogram” Th2 cells already imprinted to defend against parasites into the form specialized in defending against viruses. And what’s more, the “new” cells (“Th2+1” cells) retain some of their original properties, producing gene regulators suitable for both parasite and virus defense. Apparently, therefore, the cells are not simply transformed, but “learn to do so.” The resulting new mixed form is not a short transitional state, but can still be detected in the “memory” of the immune system months after the viral infection has subsided. The surprising results will be published by the journal Immunity: online on January 14, in the print edition on January 29. The publication can be downloaded at http://www.cell.com/immunity/newarticles. Since 2007, Max Löhning has been investigating the cellular and molecular basis of immunological memory and its functional properties as part of his Lichtenberg Professorship funded by the Volkswagen Foundation. The current results have fundamental importance for the understanding of “learning processes” in T cells and immune cells in general. In addition, this results in various biomedical application possibilities. For example, it may be possible in the future to “reprogram” T cells that are mistakenly imprinted to defend against parasites and contribute to the development of allergies and asthma into the new mixed form, thereby weakening their allergy-enhancing properties. “We are currently exploring this therapeutic application to causally combat allergies and asthma,” says Professor Löhning. Original publication Hegazy, A., Peine, M., Helmstetter, C., Panse, I., Fröhlich, A., Bergthaler, A., Flatz, L., Pinschewer, D., Radbruch, A., Löhning, M.: Interferons direct Th2 cell reprogramming to generate a stable GATA-3+T-bet+ cell subset with combined Th2 and Th2 cell functions. Immunity (2010), DOI: 10.1016/j.immuni.2009.12.004 Contact Prof. Dr. Max Löhning Medical Clinic for Rheumatology and Clinical Immunology Charité – Universitätsmedizin Berlin German Rheumatism Research Center (DRFZ) Charitéplatz 1 10117 Berlin Phone: 030 28 460 760 E-mail: [email protected] Background Lichtenberg Professorships With its funding initiative “Lichtenberg Professorships”, the Volkswagen Foundation provides an impetus for opening alternative qualification and appointment paths at German universities. The guiding idea behind this initiative: to promote outstanding scientists in connection with innovative fields of teaching and research and, at the same time, to contribute to raising the profile of German universities – in the interest of Germany as a center of science and research. The Lichtenberg Professorships are thus intended to set thematic as well as structural and research policy accents in one go. Since 2003, the Foundation has established 26 such professorships at 18 German universities. Contacts Volkswagen Foundation Press and Public Relations Phone: 0511 8381 – 380 E-mail: [email protected] Lichtenberg Professorships Support Initiative Dr. Anja Fließ Phone: 0511 8381 – 374 E-mail: [email protected] The text of the press release is available on the Internet at http://www.volkswagenstiftung.de/service/presse.html?datum=20100114. Illustration of the “reprogramming” of T helper cells by viral signals: a virus-infected … Illustration free for use in connection with the press release (rights of use with Prof. Dr. Max Löhning, Berlin). None Features of this press release: Biology, Medicine supraregional research results, scientific publications German Cells At Work Helper T Cell.

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