All day, every day

Whether we are sitting at our desks, playing sports, or watching TV on the couch, our immune system is working to protect us – 24 hours a day, seven days a week.

Our bodies are regularly exposed to external agents. To safeguard itself , our body uses a sophisticated and complex system of protection mechanisms, known as the immune system. There are several defence centres spread throughout the body, which make up this network. The largest of them can be found in the gut – home of the gut microbiota – and constitutes 80% of the entire immune system.

The human immune system

If the body defence does not work properly, infections, allergies and autoimmune diseases can be the result. BioGaia L. reuteri products contribute to a normal microbiome. BioGaia L. reuteri products support the microbiome and the normal function of the immune system


Mucous membrane in the nose and throat

External agents/Intruders can also enter the body via the air we breathe. So, the nose and throat have their own defence barrier – the mucous membrane. In the nose, this is covered with cilia, tiny hair-like projections that move back and forth, quickly transporting foreign particles out of the airway. In addition, there are plenty of cells in the mucous membrane that destroy intruders and stimulate a specific immune reaction.



Foreign intruders enter the body via the mouth, whether inhaled or ingested, they first encounter the immune system’s doorkeepers – the tonsils. The surface of the tonsils has several pits, in which food waste and pathogens can accumulate. These lead to deeper lymphatic tissue where lymphocytes (a type of white blood cell) then deal with them and store the uninvited guests’ makeup in the immunological memory.


Lymph system

The knot-like thickenings in the lymph channels have a filtering function and also contain various defence cells. It is here that white blood cells come into contact with intruders, mature into powerful defence cells, and then multiply.


Thymus gland

The thymus gland could be described as the school for the body’s bodyguards and is especially active during childhood. So-called T-cells are trained here, and they play an essential role in the organisation of defence against specific microorganisms. They learn to distinguish between the body's own and foreign structures to prevent the immune system from attacking its own cells.



The skin is our body’s protective outer cover. Untouched, it represents an impenetrable barrier for most external agents. As in the intestines, healthy skin flora inhibits the growth of harmful microbes. In addition, the epidermis contains numerous so-called Langerhans cells, which can absorb and destroy them. They, too, quickly set off a specific immune reaction when they come into contact with something potentially harmful.



The spleen is a fist-sized organ with a good blood supply located beneath the diaphragm in the left upper abdomen. As part of the immune system, it acts as a kind of storage centre for primary defence cells. Scavenger cells and lymphocytes, a subgroup of white blood cells, multiply there too. If the body sounds the alarm, lymphocytes flow out from the spleen via the lymph fluid directly to the intruders at hand.



Home to 80% of all immune cells, the gut is considered the centre of the immune system. These immune cells constantly communicate with the intestinal bacteria, providing continuous training stimuli to the immune system. The small intestine also contains accumulations of lymph nodes called Peyer's patches, where most antibodies are formed.


Mucous membrane in bladder and genitals

The mucous membranes in the bladder and genitals are also potential entry points for intruders. As in the skin, these mucous membranes contain numerous immune cells that stimulate a specific immune reaction to protect the whole organism.


Bone marrow

Some call the bone marrow the birthplace of our immune cells. This is where stem cells are located, from which all blood cells are formed, including white blood cells. Here, the various cell types within the immune system, such as scavenger cells, mast cells, granulocytes, natural killer cells, and T and B lymphocytes, are formed in several steps.

Quiz – are you an immunity expert?

Your immune system works around the clock to keep your body safe. But how much do you know about this complex system? Please don’t take it for granted! Fill-in the BioGaia Immune System Quiz instead and find out!

Answer the questions test your knowledges.


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