More on the Immune System

Last week we had a quick overview of the immune system, looking only at two of the supposed five parts – the innate system and the adaptive, or acquired, system. In knowing more about how the system works to protect us, we can find ways to nurture and protect it in return.

Photo: John Barkiple on Unsplash

Our understanding of the immune system was established in 1915 and developed somewhat until 1950, when we recognized the two parts of it. This is what is still taught in schools and appears in textbooks. Since then we have come to understand three other parts and how they interact.

The Two-Box Model of the Immune System

When a virus first comes in, the innate system meets it and creates non-specific strategies to start the fight. Their weapons are macrophages to eat them, and white blood cells that just start shooting at everything. These exist in all that lovely goo that resides in the eyes, nose, mouth, and the lining of our interior cells. This is the first 72 hour response that begins immediately on contact with an invader.

All the while, the adaptive system has been building up for the fight, generating antibodies. These are very specific, because while the fight has been going on at the front, these guys have been figuring out exactly who the enemy is and how it behaves. Their weapons are the B and T cells we talked about last week. This is the “2 box model” of the immune system.

New Discoveries

Between these two is the interferon system (IFN). First identified in 1957 by virologists Isaacs and Lindemann, the interferon was understood as single cytokines or cell signalling proteins. They numbered them in Greek, which is always cool and impressive.

What they found was that these signalling proteins were what actually woke up the specifics of the adaptive system and allowed it to identify and compare the new enemy with others that had already attacked.

What has been discovered more recently is that the interferon system is also a modulator that allows the body to know when to shut things down (once the virus has been defeated) so that it doesn’t continue generating antibodies that could begin to attack the body’s healthy cells. This is the difference between a natural inflammatory response and the so-called cytokine storm that doesn’t have the shut off valves.

The Microbiome

Over the last 20 years we have come to appreciate the fourth sub-system: the microbiome. This contains all of the lovely bugs that keep us healthy. To date, it is believed that we contain about 10 trillion bacteria in the gut and throughout the body, and possibly another 100 trillion viruses (the virome). So we’re not “mostly water” after all. We’re mostly bugs.

This is a brand new area of health research. They are investigating this now because the ratio of bacteria in our body apparently determines our level of health. (More on this in about 50 years.) People in the field of gastroenterology consider the gut and its microbiome to be your first brain.

This system, as we’re finding out, communicates intimately and directly with our neural system – the nerves and the second brain. Dr. David Perlmutter talks about this important connection in his book Brain Maker. The state and health of the gut directly affects brain health (and mental health).

In addition, the microbiome is communicating with the innate immune system, the adaptive system and the interferon system, each of which is also communicating with the others. Each one is also modulating all of the others. This is likely only the beginning of our understanding of the immune system. It is a highly complex and beautifully choreographed system.

So, now, how do we look after this incredible system?

I’ll be going into detail next week, but it likely won’t surprise you. It goes along the line of eat well, sleep well, exercise and keep your stress down. We’ll discuss more specifically how these things work to protect your body and your immune system as we move forward into a post-COVID world.

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