How do you build a system that can successfully fend off external attacks? You package it from the get-go with a bulletproof defense mechanism. Plenty of such custom designs fill our day-to-day lives. In the human-made universe, computer systems come with malware detection software. Internet systems have two-factor authentication. Phones have (fingerprint) passwords. In the world we've inherited, the Earth has an ozone layer, the human body comes equipped with an immune system, and the brain has its sense of humor.

The immune system and its inner workings are in the COVID-19 limelight. It's all for a good reason. Lacking effective medical interventions to control the COVID-19 pandemic, highly trained medical professionals had to step back and allow the immune system to open up the bag of tricks and fight the battle on its own. Just that medical experts didn't entirely step back, they took notes from the battlefield and tried to learn the tricks of the trade.

Welcome to The Command Center

Interdisciplinary research is a relatively new practice. For a long time, body systems were studied in isolation. This solitary working style is particularly ineffective when applied to interconnected mechanisms like the immune system. With limited observations, scientists could only draw partial conclusions.

The body comes equipped with different functional systems, all reporting back to the command center. Think of the brain as the command center that reports news and directives throughout the body. The nervous system is the messenger, a network that carries messages to their destination. To block off biological noise, the brain developed a few barriers that separate and limit its susceptibility to the immune system. If body systems had a trade agreement, the brain would be exempt.

We all know the brain has its smarts. In the fight for survival, the brain equipped itself with a proprietary immune mechanism. This kind of decoupling of body/brain immune systems would make you think the two systems do their job in isolation. Scientists are debunking this myth. It turns out the (peripheral) immune system is not self-regulated as previously thought, but functions in close association with the nervous system. 

An Elegant Puzzle

Many questions remain unanswered about how the brain's nervous system collaborates with the immune system. We’re starting to glean more insights into their synergies, mostly based on their similarities. The two systems have a lot in common, as they both operate on top of information relaying mechanisms. These high-speed systems - a page from the Wolf of Wall Street - can communicate information to remote cells with extraordinary specificity and diversity.

Dialogue between the brain and the immune system is a two-way street. Information exchanged between the immune and nervous systems allows the immune system to engage the whole body in the fight against infections and enables the nervous system to regulate immune functioning. Similarly, immune cells play a role in memory and learning by influencing the plasticity of nerve junctions during child development and adulthood.

Any alteration in one of the immune systems can impact the functioning of the other. Changes in the communication pathways between the immune system and the nervous system can account for many pathological conditions initially attributed solely to organ dysfunction. I am referring here to psychiatric disorders like depression and immune-mediated diseases like cancer.

What is the Immune System 

The immune system is more approachable than the nervous system, so we've been able to observe and decipher some of its secret codes. If the brain is the CEO of the Body, the immune system operates the COO office where it runs three sequential operations: detect, triage, eliminate. Firstly, the immune system scans the body 24/7 to detect external agents - pathogens such as viruses or parasitic worms. Secondly, it triages these foreign agents and distinguishes them from healthy tissue. Lastly, it eliminates the agents that pose a health threat.

Like any reputable COO, the immune system runs its multi-step strategic operations through layered defenses of increased specificity. A pathogen's journey starts at ground zero: a physical barrier like the skin or mucus. If a pathogen breaches these physical barriers, it stumbles into the innate immune system. The innate immune system provides an immediate and general response. If pathogens evade the innate system, the third layer of protection, the adaptive immune system, is activated by the innate response.

The adaptive immune system has a high-fidelity reaction. Pathogens can rapidly evolve and adapt, and thereby avoid detection and neutralization by the immune system. Just like the adaptive pathogens, the adaptive immune system adjusts its response to better recognize the mutating pathogen. Once a pathogen gets eliminated, the immune system memorizes the blueprint of what worked during the enhanced response. A memory of past incidents allows the adaptive immune system to mount better/faster/stronger attacks during future encounters with the same pathogen.

Why You Should Care 

COVID-19 is a jack-of-all-trades disease with surprising long-term consequences. The COVID-19 death toll is devastating but could be a page in a much larger story. We don't know the disability toll yet. What we do know is that the body is a forgiving system and works like a charm. It has a natural elasticity and can recover from being fed incorrect information coming from many sources: food, entertainment, our physical and social environment. But over time, the body's ability to deal with incorrect information weakens. Just like the Earth is losing its ability to keep the seasons in check, our immune system is losing its ability to self-regulate.

We are looking at the immune system to save the day, but it can only put up half the battle. The brain's immune system should help us paint the full picture. We already know that when the nervous system is weakened, strong side-effects percolate into the immune system. Prolonged psychological stress increases the risk of infection via viral respiratory pathogens. The brain's immune system is also involved in respiratory illnesses like asthma and chronic cough. Also, some of the hormones controlled by the brain have a direct impact on the immune system. High testosterone in men can weaken the immune response and lead to dull results from vaccines like the influenza vaccine.

Until we better understand how the brain communicates and influences the immune system and vice-versa, it's safe to assume the immune system dances to the brain’s tune. What’s even more surprising is that 70% of the immune system is found in the gut - call it the control tower. Whether observed in isolation or as a pair, both immune systems go off color when digesting poor foods, stress, smoking, and alcohol. It sure can't help that the US is one of the fattest nations on Earth, with the highest rate of childhood obesity.

For now, we’re all trying to keep body and soul together. If we’re given a new lease of live, why not make it the healthiest, happiest life yet? There are choices you can make that will reinforce this mantra. It comes down to the basics: time with friends and family, meditation, healthy food, physical exercise, time in nature, a fulfilling job. It's the little things that allow the brain and the immune system to take charge, self-regulate, and do what they do best: protect the fortress.