The immune system – tasks and function

Our immune system works day and night: It is constantly being attacked by bacteria, viruses and fungi from our environment. As a rule, we don’t notice anything about it; this is ensured by a complicated system in which the defence cells of the white blood cells, soluble proteins and organs form a team. The players can complete a “task” together or “get to work” individually. All mechanisms are intertwined and influence each other.

Two defence systems of the immune system

The immune system includes the thymus and spleen as organs, as well as tissues such as bone marrow, lymph nodes, tonsils, and the lymphatic tissue of the gut. Immune cells are found in almost every tissue in the body. A weakening or even a defect in the immune system can have severe consequences for the body.

The body has two different defence systems at its disposal: on the one hand, the so-called non-specific defence is already given to every newborn. It is immediately directed against a wide range of foreign bodies. On the other hand, for the specific defence, they first have to learn against whom they should take action – but then, all the more effectively.

 

The non-specific immune defence: the fast generalists

The players of the non-specific defence take over the acute use. There is no fiddling around here. Everything foreign is attacked. They destroy virus-infected and tumour cells, inhibit inflammation, fight off viruses by preventing their protein build-up and slow down cell growth. The white blood cells or leukocytes are the supreme commanders of the non-specific immune defence.

An influential group is the so-called scavenger cells, also called phagocytes. This subset of white blood cells can recognize specific structures on the pathogen’s surface as foreign. Some can do even more: They not only dissolve the invaders but also pass on information about the enemies, the so-called antigens, and thus enable the specific defence to “learn” the characteristics.

Sometimes, however, the scavenger cells overshoot their target when they fight harmless grasses or food as dangerous invaders or reject a transplant as a foreign body.

The specific immune defence: the trained specialists

Here, two participants assume the primary responsibility: immunoglobulins and lymphocytes. Lymphocytes are the smallest white blood cells (leukocytes) formed in the bone marrow and the lymphatic organs: the thymus, spleen, tonsils, Peyer’s patches, and lymph nodes. Around 95 per cent of the lymphocytes are also stored there. If necessary, they can be released into the bloodstream.

B lymphocytes and T lymphocytes

There are two types of lymphocytes: B lymphocytes and T lymphocytes. These have different places of education, different tasks and different appearances. Both subtypes have short-lived lymphocytes that are only active for seven days and long-lived lymphocytes that serve 500 days. The latter work as “memory cells”. They can remember the causative agent of a survived infection. In a renewed infection with the pathogen, they can react much faster and more effectively.

Immunoglobulins – Antibodies

The lymphocytes are supported in their work by the immunoglobulins. If the body perceives a substance as foreign or “antigenic”, it defends itself against it with so-called antibodies, also called immunoglobulins, in technical jargon. These are proteins that are produced by the immune system. Simply put, they can dock onto foreign bodies and destroy them.

This happens in the following way: if an antigen is recognized as foreign, the immune cells produce antibodies that match this antigen exactly – like a key in a lock. This antigen-antibody complex ensures the formation of further proteins. This leads to the direct destruction of the foreign substance. Or else: The antigen-antibody complex calls for help from specialized immune cells that there is a foreign substance in the organism. These specialized cells destroy the complex and remove it from the body.