The wonderful human immune system - lymphocytes
Lymphocytes learn to recognize their "enemy".
In my work as a physician, I repeatedly find that many people think they are defenseless against pathogens from the outside world. They see the only supposed way out in taking medications that can quickly kill these pathogens.
So it is often bacteria, viruses or even fungal infections that cause us problems. In rare cases, it is also parasitic diseases such as amoebae, etc., that cause problems.
The good news is - we are not helpless against these attacks. Our immune system is an incredibly sophisticated system with various bulwarks to protect our health. We've already heard about macrophages, which are part of the innate immune system and one of the first barriers to disease germs. Read more about them here. If pathogens manage to infect body cells despite macrophages and other "sensor cells" (such as dentritic cells), other immunocompetent cells may come into play. Activation of the T lymphocyteYou have probably heard of lymphocytes. Lymphocytes belong to the adaptive immune system, which means that this immune system can adapt very specifically to a particular pathogen. It is capable of learning. We distinguish between T lymphocytes and B lymphocytes. The T lymphocytes, in the form of "cytotoxic effector cells" or "killer cells," can recognize cells attacked by viruses, for example. For this purpose they have a Receptor on your cell membrane.
See Figure 1.Activation of the T lymphocyte This receptor of the lymphocytes can then recognize certain protein fragments (peptides) of pathogenic agents. These pathogen peptides are in turn "presented" by infected cells on their cell surface. The "diseased" cell thus signals "Hello, I am infested." but sacrifices itself in the same way, since it can be destroyed by the killer cells. The reproduction of bacteria or viruses is thus deprived of the ground. This is called the cellular immune response. B lymphocytes
(Figure 2) also have receptors in their cell membrane. These receptors can also recognize components of pathogens. Unlike T lymphocytes, however, they do not intervene directly. Instead, B lymphocytes produce so-called antibodies. This is called the humoral immune response. These antibodies are very similar to the receptors in their membrane, except that they can "swim around" freely in the blood. There they can bind pathogens or their toxins (poisons). If these pathogens (antigens) are bound by antibodies, they can be eliminated more easily. The B lymphocytes that produce antibodies are called plasma cells. At the same time, so-called memory cells are also produced. They can immediately produce antibodies when the same pathogen infects the body, sometimes years later.