The immune system:

One of the most important tasks of our immune system is to eliminate intruders, such as bacteria and viruses that have entered our body, and to ensure that we recover after an infection. The immune system also plays an important role in getting rid of harmful body cells, and thus in preventing diseases like cancer.

The human immune system basically consists of 3 parts:

The first line of defence is formed by physical barriers such as the skin and mucous membranes, but also by certain substances in, for example, our saliva and gastric juice that can kill intruders.

The second line of defence is our innate immune system.  This system is, for the most part, already present when we are born and can take action very quickly. The innate immune system consists of various cells, such as granulocytes, monocytes-macrophages and dendritic cells.  These cells come into action when a bacterium or virus manages to enter the body despite the physical barriers.  In most cases, the cells of the innate immune system succeed in killing and removing the invaders, but if they fail to do so, the acquired immune system is activated.

The third line of defence is the acquired immune system. The acquired immune system consists of other cells than the innate immune system, namely the lymphocytes (called -B and T cells), and is therefore not activated right away. The acquired immune system develops over the course of life. A big advantage of this immune system is that it will come into action faster if a similar pathogen enters the body again. This mechanism is also used in vaccinations. It is called the memory of the immune system.

When the immune system is activated, the cells of the immune system will start to produce various cytokines. These are molecules that allow the cells to talk to each other and to other cells in the body. This way the cells know where to go to, are activated and start multiplying. These cytokines also affect other parts of the body. Among other things, they cause fever and increase the blood flow at the area of the infection. The most well-known cytokines that are produced during inflammation are IL1, IL6, IL18, IFN and TNF. Cytokines are produced by both the innate and the acquired immune system.

Once the infection has been subdued, the immune system will usually return to its normal state. However, some diseases cause the immune system to malfunction.

If the immune system doesn’t work well, you will be exposed to too many infections and have more chance of getting cancer, for example. We call this an immune deficiency or immune disorder. If your immune system is working too hard or attacking your own body, we call this an autoimmune disease or an autoinflammatory disease.

If something goes wrong with the innate immune system, an autoinflammatory disease may develop.  People with an autoinflammatory disease will often suddenly develop a fever and inflammation in various places such as the joints, abdomen, lungs or skin. The symptoms are very similar to an infection. This is because the cells of the innate immune system suddenly jump into action without there being a real intruder. The immune cells will then start to produce a lot of different inflammatory substances (cytokines), such as IL-1 and IL-6. For a number of autoinflammatory diseases, we know that there is a flaw in the genetic predisposition (DNA) that causes the cells to go haywire (see also the part on genetics), but for some diseases the cause is unknown. Examples of autoinflammatory diseases are periodic fever syndromes and the systemic form of juvenile arthritis.