NuroseneNov 29

Expanding Our Concept of Immunity

If I were to ask you to explain your immune system, could you do it?

Graphic of an outline of a human with the text 'the immune self' in the center

I bet you could. Most of us have at least a general understanding of what it is and how it works. You might know about white blood cells, and antibodies, and maybe even the fact that it “remembers” certain pathogens for a stronger and faster response next time. Get chicken pox once, and you’ll never get it again.

You’d likely describe it as a defense system protecting our bodies from foreign invaders such as viruses, bacteria, fungi, and parasites. Catch a flu bug, for example, and your immune system goes to work trying to eliminate it via fever, B-cells, and T-cells.

This is the traditional model, and it is all true.

But it’s not the complete story.

Immune theory has expanded. What was once reserved to the basic premise of self vs. non-self is being replaced by a much more symbiotic relationship between an organism and its environment.

If anything, it’s better to describe it as a communication system that processes information from both within and without, and reacts accordingly. It both receives and sends information to other parts and systems of the body.

It does not sit idly by waiting for some non-self entity to breach the outer defenses. It’s actively involved on a day-to-day basis.

Preparing for Battle…

Before the enemy arrives.

We’ve historically thought of immunity as a reactive defense system: body encounters foreign pathogen, and body reacts by sending white blood cells to kill it.

That does happen — and thank goodness for that — but the immune system is doing so much more than we ever thought possible.

Acute stress as registered by the brain, for example, can send a call-to-arms to the immune system before anything has happened. It’s not a response to a cut, injury, or pathogen. It’s preparation for something that might happen in the near future. And it’s driven by an external — rather than internal — factor (whatever is causing the stress, in this case).

Our “fight-or-flight” response to acute stress floods our system with stress hormones like cortisol, and those hormones do more than just prepare us to defend ourselves physically or flee. They actually mobilize our immune cells, too.

Multiple systems are communicating with each other in dealing with an external stimulus. We’re prepared and ready for the possibility of an injury instead of simply jumping into action only after it occurs.

It’s the difference between setting up a field hospital before a battle, or waiting until after the casualties start to arrive.

But it goes beyond simply getting ready.

Responding to the Environment

The immune system becomes both judge and jury of defensive strategies and offensive attacks. An altering dynamic governed by a level of tolerance with complex relationships.

The outside pillars of a court house framed by red autumn leaves

This can be considered a second-order response to the immune system’s primary communicative and cognitive functions.

And this phenomenon is shared across species, too.

In one study, researchers discovered that stress hormones (corticosteroids) act cooperatively with thyroid hormones (TH) to accelerate tadpole development.

Research like this has taught us that environmental stressors can alter the function of certain genes which then affect the rate of development.

Inside, outside, defense, offense, development. It’s all connected.

This goes against much of the last 50+ years of a gene-heavy bias, where the building blocks of life were thought to be the main drivers of development.

And while no one is doubting the importance of genetics, we are beginning to see that they are a lot more influenced by our environment than we had ever imagined.

If COVID-19 has taught us anything, it’s that the biology and immune function of an individual is often predicated on the biology and function of the community.

What does that mean for us as a species moving forward? New research is attempting to answer just that. Stay tuned.