Definition
T-lymphocytes are cells of the immune system and can be found in the blood. The blood is composed of blood cells and blood plasma. The blood cells are further divided into erythrocytes (red blood cells), leukocytes (white blood cells) & thrombocytes (blood platelets).
T lymphocytes are a component of white blood cells and can be further subdivided into T killer cells, T helper cells, T memory cells, cytotoxic T cells and regulatory T cells. The T-lymphocytes are colloquially also called T-cells. The letter “T” stands for the place of maturation of the T-lymphocytes, namely the thymus.
It is located in the upper part of the thorax and is an important organ for the immune defense. The T-lymphocytes are assigned to the adaptive, i.e. the acquired immune defense. This means that they need some time to be able to react to pathogens, but as a consequence they can do so in a more targeted and thus usually more effectively than the innate defence.
Anatomy
The T lymphocytes have a spherical shape and grow to about 7.5 micrometers in size. They consist of a round, slightly dented cell nucleus surrounded by cytoplasm. In addition, ribosomes can be found increasingly in the cell interior.
Tasks
The main task of T-lymphocytes is the immune defense. The non-activated T-lymphocytes spread throughout the entire organism via the blood and lymphatic tissue, controlling unnatural changes in the body’s own cells. Such pathological changes can be caused, for example, by pathogens that have penetrated the body or by mutations of the genetic material.
In adults, about 95% of non-activated lymphocytes are stored in the thymus, spleen, tonsils and lymph nodes. If pathogens such as bacteria or viruses enter the body, they are first recognized and bound by other defense cells of the immune system. These include macrophages, B cells, dendritic cells and monocytes.
Only the combination of these defense cells and the pathogens trigger an activation of the T-lymphocytes. The T-lymphocytes can then finally recognize the pathogens and classify them as foreign. However, each T-lymphocyte can only recognize very specific pathogens.
The identification between the pathogen and the T-lymphocytes is carried out via so-called MHC molecules, which are located on the surface of the pathogens, and certain membrane components of the T-lymphocytes. If these two surface features match according to the lock-and-key principle, the T-lymphocytes are activated and can react to the pathogens accordingly. However, the different subtypes of T lymphocytes react to the pathogens with different mechanisms, depending on the type of pathological change.
For example, the T-killer cell reacts by directly destroying the pathogens, while the T-helper cells attract further immune defense cells by releasing messenger substances, which in turn are responsible for the elimination of the pathogens. The regulatory T-cells, on the other hand, primarily prevent the pathogens from spreading to other endogenous cells. Cytotoxic T cells ensure the destruction of pathogens by releasing various enzymes. The T-memory cells do not contribute directly to the elimination of pathogens, but nevertheless play a decisive role, as they store the properties of specific pathogens. This storage enables a faster and more targeted immune response to be triggered the next time a pathogen enters the body.
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