From birth, the so-called non-specific immune system works - the specific is acquired only in the course of life. It is only fully developed at the age of 10 to 12 years. This is the reason why children are very susceptible to infection. But the immunological memory learns with each infection ...
How does the body's defense work?
Since most attacks occur from the outside, a healthy and intact skin is an important prerequisite to prevent the ingress of germs. Body openings such as the mouth and nose have a whole range of possibilities to prevent germs from advancing further: mucous membranes are covered with cilia, which can carry invaders back towards the "exit".
The secretions of the mucous membranes (secretions with antibacterial properties) bind germs and try to destroy them early. For example, if germs have already penetrated into the stomach with food, the stomach acid with its destructive power comes into action.
Protective shield immune system
However, if a germ has managed to overcome all barriers and penetrate the bloodstream or into a body cell, the body's own immune system is required. The immune system has a whole host of sophisticated - less specific and highly specific - defense mechanisms that it can use as weapons against the invaders. Thus, the body's defense is prepared for almost all possible attackers.
It is particularly strong where aggressive, alien substances are most likely to be found: in the skin, in the mucous membrane and in the blood, in which an always ready, flexible "immuno-patrol" is on the way through the entire body.
The nonspecific and specific immune system
In the first line of defense are the so-called Fresszellen. They are part of the nonspecific immune system and eat up everything that they recognize as foreign. It is also they who raise the alarm for the second line of defense, the specific immune system.
This extraordinarily efficient system of specific immune cells, which are "trimmed" to very specific pathogens, only becomes active when exactly this pathogen enters their territory. They are equipped for their use with highly effective weapons, the so-called antibodies. These find the pathogen specifically and connect with him. The pathogen is thus more easily recognized by the phagocytes.
Immunity and vaccinations
If a pathogen enters our body for the first time, the specific immune cells must first get to know it and memorize it. In a second infection of the same pathogen, they are then armed and can attack and eliminate him much faster. That is why we can become immune to certain diseases.
Immunity means that this pathogen is made harmless on second contact by the imprinted on him immune cells and the second infection goes unnoticed. The pathogen can no longer multiply and cause disease symptoms. This principle makes use of medicine in vaccinations: one exposes the body to a harmless pathogen, for example the smallpox pathogen. It is characterized by specific immune cells that keep this pathogen in mind.
Because not all immune cells have the same amount of memory, it happens that we have lifelong protection for certain pathogens, others only for a few years, and for others just a few weeks. Each specific immune cell only recognizes a specific pathogen. That's why there are millions of different immune cells, all just lurking for "their" enemy to cross their paths again.