Natural immunity and acquired immunity

The immune system rests on two main pillars: the general innate immune system (the natural immune system) and the acquired and specialized immune system. Both systems work closely together and take on different tasks.

Defense cells in tissues:

Both parts of the immune system function at different levels: First, there are special defense cells in different tissues that are directly involved in eliminating pathogens (germs). These cells belong to what is called cellular defense.

Defense cells in blood and other fluids:

Second, both the natural (innate) immune system and the acquired system also need many of the soluble substances found in blood and other body fluids. These are mainly proteins such as enzymes, antibodies, and short amino acid chains. These substances belong to the humoral defense. So both parts of the immune system (innate and acquired) employ both cellular and congenital defense strategies.

The natural immune system: rapid, effective and widespread

The strength of the general natural immune defense is being able to move and react very quickly. Ensure, for example, that bacteria that entered the skin through a small wound are detected and partially destroyed immediately within a few hours.

Since the innate immune response is not specialized for specific pathogens, it does not need a long initiation phase. Because of this broad effect, it is only able to a certain degree of stopping germs from entering and spreading in the body.

Innate defense consists of several components:

• The skin and all mucous membranes in the openings of the body, which are external barriers.

• Various defense cells of the group of white blood cells (leukocytes).

• Various substances in blood and body fluids.

External protection: skin and mucous membranes

All external and internal surfaces of the human body are a major component of the normal immune system. The closed surface of the skin and all mucous membranes form a mechanical barrier for pathogens, preventing them from entering.

Additionally, chemicals such as acid, enzymes, or mucus prevent bacteria or viruses from gaining a foothold. Movements created, for example, by hair-like structures in the bronchi (cilia) or by intestinal muscles that prevent germs from settling in the body. Tear fluids, sweat, or urine that rinse the urinary organs have a similar effect.

Internal protection: defense cells and proteins

If, despite all the obstacles, pathogens bypass the skin or mucous membranes and enter the body, then the second line of defense of the fungal system comes into play. Inflammatory cells move to the site of injury, or already existing defense cells are activated.

Soluble protein substances in the supplement system are also activated, and help to defend the body. This leads to an inflammatory reaction in which blood circulation is increased and the affected area becomes swollen and hot. Sometimes there is also a fever.

If bacteria or viruses enter the body, they can be removed immediately by macrophage cells (from the Greek pharynx, meaning: "eat food"). Two types of defense cells are the most effective: macrophages, which are found in tissues, and neutrophil granulocytes, which are found in blood and tissues.

These cells take up pathogens and digest them in the interior. Scavenger cells (macrophages) can function better if the pathogen is already distinguished by antibodies or complement system proteins. This makes the pathogen more "acceptable" to scavenger cells.

So at this point, the immune system's antibodies support the natural defense. Conversely, scavenger cells (macrophages) can aid the acquired immune system by eating and digesting specific pathogens very quickly.

Complementary system: proteins in a chain reaction

Soluble substances support the defense cells of the normal immune system. A group of nine different enzymes activate each other in a process similar to a chain reaction: one of the enzymes of the first stage stimulates several enzymes of the second stage, each of which again activates several enzymes of the third stage, and so on. This process quickly makes the defense reaction much stronger, because the production of these proteins increases in such large jumps (exponentially).

The tasks of these enzymes:

• They set pathogens, making them more attractive to macrophages.

• It works to attract other immune cells from the blood.

• Cell walls dissolve from bacteria, so that bacteria lose fluid and minerals and die.

• They fight viruses directly by destroying virus envelopes, or indirectly by destroying virus-infected cells.

Natural killer cells:

Looking for altered body cells, natural killer cells are the third important part of the innate immune system. These cells specialize in identifying cells that are infected with a virus or that have become cancerous. These cells do this by looking for changes in cell surfaces. If natural killer cells find cells with an altered surface, they dissolve them using cytotoxins, also called cytotoxins.