Tasks of the immune system
The immune system is the body’s defense system. Its task is to fend off pathogens, which essentially include bacteria, viruses, fungi and parasites. In the immune system one can distinguish between two large areas that in most cases work together.
The first area describes the innate, non-specific immune system. It is available to humans from birth and represents the first barrier in the fight against foreign bodies. As the name suggests, this immune defense is non-specialized, i.e. it consists of universal defense mechanisms to keep the invading foreign bodies in check until the specific immune system starts to work.
On the one hand, physical barriers such as the skin, mucous membranes, hair, which make it difficult for foreign bodies to enter the organism, belong to this area. On the other hand, there are also special defense cells, such as phagocytes (scavenger cells), which eat everything foreign to the body in their vicinity, or natural killer cells with the unspecific immune system. This is a series of proteins that, when activated, cling to and mark intruders and can cause them to dissolve.
The specific, acquired immune system, on the other hand, must first develop over the course of a lifetime. It consists mainly of B and T lymphocytes (white blood cells), the antibodies they produce and scavenger cells. T-lymphocytes can develop into T-killer cells and can attack foreign bodies directly.
If an intruder is eaten by a scavenger cell, the latter can pass on its signature (antigen) to a B lymphocyte. This then develops into a so-calledplasma cell and begins to produce antibody proteins that are the counterpart of the antigen. Learn more about superantigens.
These antibodies can now recognize intruder lines that carry the same antigen, attach themselves to it and thus paralyze it and mark it as prey for scavenger cells. Since this process takes several days, the specific immune system’s action is delayed. Therefore, some B-cells develop into so-called memory cells, which survive for life and continue to produce specific antibodies.
If the body is confronted with the same intruder again at another time, the specific immune system can react much faster because it still has the matching antibodies “in its memory“. The innate immune defense/immune system is present in every infant (not suffering from an immune disease) and provides a non-specific immune defense, i.e. it attacks everything foreign. An important component of the innate immune system is the so-called complement system.
This immune system consists of approx. 20 different serum proteins (part of the blood), which above all can literally surround bacteria (so-called opsonization) and activate macrophages, which then eliminate the bacteria. In addition, further body cells (namely so-called monocytes, mast cells, granulocytes as well as natural killer cells) can be activated, which lead to the elimination of the intruders.
The above mentioned barriers of the immune system, such as the skin or mucous membrane with its special cells, the epithelia, are also part of the innate defence. The cells of the innate immune defense/immune system are like a first strike force in the fight against invading pathogens. By means of a so-called major histocompatibility complex (MHC), which is present on every cell of the body, the defense cell can distinguish between friend and foe.
Most infections are recognized and eliminated by cells of the innate immune system. The cells of the innate immune system include macrophages (scavenger cells), natural killer cells, mast cells, monocytes and epithelial cells. However, these cells are not only important for the innate immune system, they can also present parts of eaten pathogens to other cells on their cell envelope (cell membrane), so that these cells form antibodies against the pathogens. This makes the pathogens’ defense even more special or specific.
