Around 1900, researcher Paul Ehrlich recognized that the body can distinguish between cells that are foreign to the body and those that are endogenous to the body. This vital mechanism enables the organism to recognize and destroy foreign, potentially threatening substances without destroying itself. In autoimmune diseases, this process is impaired.
Dysfunction of the immune system
The human immune system is a complex interplay of different cells and organs that is used to recognize and destroy not only foreign substances and pathogens, but also the body’s own cells that no longer function. Without an immune system, we could not survive for long – after all, we are surrounded by potentially pathogenic microorganisms such as bacteria, viruses and fungi. In principle, the defense processes can be disturbed in two directions; both can lead to dysfunction and disease:
- Immune deficiency diseases: The defense is not effective enough, for example, in congenital immunodeficiencies or when the immune system is incapacitated, for example, by chronic diseases or drugs.
- Autoimmune diseases: The defense works stronger than necessary and also attacks the body’s own tissue.
The immune system
Our defenses are constantly in action: they patrol the body – primarily in the form of white blood cells and the immunoglobulins they produce – in the blood and lymphatic vessels to detect potential threats and destroy the originators before they can cause mischief. To do this, it uses two systems: the innate, nonspecific defense and the acquired specific (or adaptive) defense, which work closely together:
- Nonspecific defense: This includes barriers such as the skin and mucosa that make it difficult for pathogens to enter in the first place. If the enemies have nevertheless stormed the barricades, messenger substances, e.g. so-called interleukins, are released by various cells, which – similar to a flare – signal that danger is imminent and request help. Locally, this also leads to an inflammatory reaction.
Defense forces such as phagocytes and killer cells quickly rush in to destroy everything that is foreign by means of a “hit and run” strategy. To avoid being targeted themselves, the body’s own healthy cells carry a kind of identification mark on their surface, the so-called major histocompatibility complex (MHC). With this, they can identify themselves as belonging to the body and thus remain spared from the destructive action. The majority of all infections are already successfully fought by this system.
- Specific defense: This special unit is able to act against attackers quite specifically. To do this, it makes use of a kind of criminal file in which all the bad guys who have ever been detected by the immune system are stored. This is stored in “memory cells”. Antigens on the surface of these cells serve as “fingerprints” of the crooks, which are recognized again and again by the antibodies (immunoglobulins) formed in the body after initial contact. This enables a rapid, specific defense reaction and the pathogens are destroyed before they can go into action.
Incidentally, vaccinations also work according to this principle: For example, inactive (and thus harmless) viruses are injected and the body produces antibodies against their antigens (which correspond to those of the correct pathogens). If the correct pathogen then enters the organism, it is quickly recognized and destroyed.
