One of the most memorable images of 2020 will probably be the empty disinfectant and cologne shelves in grocery stores. The entire world has been trying to maximize personal hygiene, and stay as sterile as possible to avoid the virus called SARS-CoV-2. We have been trying hard to keep the virus away from our bodies; in other words, we have been trying hard to keep our first line of defense as strong as possible. Hence, we have little idea how well our next line of defense, our immune system, will test against the COVID-19 disease. While trying to remain as sterile as possible, we must also consider that our body is actually a reservoir of microorganisms and that we live with trillions of bacteria and viruses. In fact, our defense mechanisms against the virus that we try to keep away from our bodies depends to a certain extent on our relationships with the other microorganisms we live with. They train and guide our immunity and determine our resistance.
Our immune system is our most important safeguard against external threats and foreign bodies. So, how is it possible that this sea of microorganisms, which is at least as large in size as our own cells, lives in our bodies despite this system, which is responsible for destroying external threats? In fact, this union is the result of peace and partnership that has lasted for millions of years. Our microbiota, which forms the microorganism communities residing in our body, and our immune system develop together upon our birth, and our microbiota teaches our immune system how to recognize and respond to external threats, such as vaccines. On the other hand, our immune system does not attack our ‘friendly’ microorganisms, allowing them to live in our bodies. So much so that some scientific studies revealed that our immune cells recognize beneficial bacteria as friends from their peptide molecules, and they do not harm them.
On the other hand, the microbiome not only trains our immune system and keeps it prepared, but also directly participates in the defense against external pathogens. An interesting example is that immune cells in the lung work together with the microbiome to recognize the influenza virus (which we might consider a relative of the novel coronavirus). The immune cells patrolling the lungs quickly detect the virus and start to defend against it by producing antibody proteins that recognize this virus. Studies have revealed that the metabolites produced by certain bacteria in the microbiome enable the production of these antibodies. Moreover, experiments conducted on animals have concluded that individuals with an impaired microbiome cannot have this immune response, while individuals with a healthy microbiome can quickly recover from the disease.
The balance of the microbiome with our body and ensuring a diverse and rich microbiome community play a key role in having a strong immune system. The key to keeping our microbiome healthy, which supports strong immunity, lies in proper nutrition. Similar to us, our microbiome is shaped by what we consume. We need to build up an immune system that is capable of issuing strong responses to protect against infections, therefore, we need a microbiome that is balanced and diversified by a proper diet.