Each of us is born with an intricate defense system that works to protect our bodies against illness and disease. You probably already know what this is, but I’ll tell you anyways. It’s your immune system. It’s made up of a network of cells and organs that work together to detect potential threats within your body and react to fight those invaders.
If all is working correctly, invaders are identified and the appropriate response is mounted. This also means our own cells are recognized as non-threats and left alone. Our immune systems mature and evolve with age, just as we do. They are vulnerable in infancy, strengthen into adulthood, and become vulnerable again as our age advances even more.
What’s Going on in Your Immune System?
The immune system, though complex, can be broken down into two overarching components – innate and adaptive immunities.
Just like your entire immune system, your innate immune system is also comprised of two components: physical barriers and innate immune cells.
Physical barriers include our skin, stomach acid, and the hairs in our noses and ears that catch potential threats before they make their way too far into our bodies. They may seem ordinary – and maybe evenly unsightly – but these physical barriers play a big part in keeping your body healthy! Without them, your immune system wouldn’t stand a chance of keeping you from getting infections!
Innate immune cells, called neutrophils and monocytes, are also critical for your immune function. These cells act like your body’s first responders. They live right in your skin, so they are always first on the scene of intrusion and they work to gain immediate control of the situation, before sending for the appropriate backup from your adaptive immune system.
Your adaptive immune system does just what it sounds like it does: it adapts! It is made up of two groups of cells, B-cells and T-cells, which have special memory functions. Any time your body encounters a bacteria, virus, fungus, parasite or cancer cell, a B-cell or T-cell takes a kind of teeny-tiny molecular picture of it. If that dangerous germ or type of cancer cell ever pops up in your body again, that B-cell or T-cell recognizes it immediately and mounts a vicious attack.
To understand how the innate and adaptive immune system work together to protect your body, it can help to imagine the outside of your body (skin, lungs, GI tract) like the walls of a well-defended castle.
The walls themselves are your skin. They keep most intruders out by just being there! But they also have a bunch of tricks up their sleeves to make sure no one slips past and into the castle unchallenged.
For example, they are lined with barbed wire (those little nose and ear hairs!) that trap intruders that think they’ve scaled the walls and found a way in. And along the top of the wall, or peaking out through windows, are archers (neutrophils), ready to fight off any intruders that make it to, or even past, the walls and the barbed wire.
Each archer is also outfitted with a distress beacon. If any intruder makes it past the wall, and the barbed wire, they light the beacon and call highly trained knights (T-cells) and squires (B-cells) to fight off the intruders.
Could this be the next greatest action movie I’m describing? I’ll start writing up the script.
In the meantime, know that both of these systems (innate and adaptive immunity) are present starting in the womb and develop throughout your lifetime. And both are essential to the effectiveness of the immune response.
Immune System Lifecycle
In the womb, your immune system doesn’t have a ton to do yet. Your mother’s body and your placenta help keep you sheltered from essentially all danger.
When you are born, though, you thrust from the relative safety of the womb into this big bacteria-filled world and your little immune system has to get to work. Now, it is given a boost up, thankfully, with Mom giving you some of her antibodies through the placenta just before your born, some of her helpful bacteria while you’re being born (there’s a difference if delivered vaginally vs. C-section), and some more of her antibodies via her milk just after you’re born.
It’s a good thing, too, that you get help. Even with moms giving babies’ immune systems a hand up, babies still often struggle to fight off infections. The highly vulnerable young immune system is what was to blame for high rates of infant and childhood deaths in previous generations.
Luckily, today, this is less of a problem. Additional help from hygiene and vaccines gives most babies’ immune systems the upper hand until they can build themselves up enough to take over the defenses for themselves.
This build-up of immature immune systems occurs by the immune system just encountering all kinds of new germs. These encounters let the immune system flex its young muscles, with neutrophils multiplying and taking up their positions in the skin and T-cells and B-cells collecting more and more names for their hit lists.
This beefs up the immune system big time. The innate immunity learns to better identify different substances from outside the body and the adaptive immunity becomes equipped with the necessary information to fight off more and more types of dangerous substances.
Ages of Aging
That all sounds good, right? As you age, your immune system gets better at defense, and as you start going down the other side of the hill you should be as prepared as ever to fight off infections and cancers. Right?
Wrong. Just as your body gets stiffer and slower year after year, your immune system also becomes slower. The innate immune cells have a harder time differentiating between various invaders and determining healthy cells from unhealthy cells.
In order to understand how your immune system ages, it’s important to know how cells age in general. (After all, your immune system is made up, primarily, of cells.)
At its most basic level, aging is the result of cell malfunction. And cell malfunction is the result of cellular damage.
See, you have trillions of cells, all dividing over and over again, copying their unique DNA sequence and passing on their roles to newer and younger cells. Because this happens so frequently, there is the potential for mistakes to occur, or mutagens from the environment to damage DNA strands.
Since healthy DNA is required for cells to function properly, unhealthy, damaged DNA causes cells to malfunction. And you age.
Effects of Aging on The Immune System
So, what happens to your immune function when your immune cells become damaged and age?
A few things!
Your Infections Spread More Quickly
First, when you age, your innate immune cells, like neutrophils, lose their ability to direct themselves to the infection site – they’re like drivers who have lost control of the wheel. If you’ll remember, the innate immune fighters are the first responders. If they don’t show up on time because of poor driving ability, the infection can get out of control quickly.
You’re More Prone to Autoimmune Diseases
Second, adaptive immune cells become more and more prone to errors. T-cells fail to fight infections they’ve been trained to attack or start attacking the wrong cells (sometimes even your own body’s cells!). And B-cells don’t recognize as well when they are needed to help fight.
Your Body is Less Able to Recognize Infections
Lastly, your adaptive immune cells begin losing their ability to learn and store information about new infectious bad guys. This results in a slower, weaker, less adaptable team of backup immune cells.
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Consequences of Immune System Aging
All of these factors add up to an immune system that is quite experienced, but also, unfortunately, quite tired. And this general decline in function at all levels of your immune system means your body is less equipped to fight off infections and diseases the older you get.
It will still try to fight, though. And that combination leads to a couple of serious problems for your health.
The first problem, of course, is that you experience more infections. That is a natural, obvious, consequence of a poorly functioning immune system.
The second problem, the development of chronic inflammation, is less obvious, but really logical. To explain why, let’s go back to the castle analogy.
What would be the logical response for an archer if, after they set off their distress beacon, the knights and squires don’t come? Set off another one, right? Or get their neighbor to set off theirs. Something – anything to get the knights to come help before it’s too late.
That is exactly what the innate immune system does when, as you age, your B-cells and T-cells slow down and stop showing up and fighting the way they should. They pump out more and more distress signals to the body.
Unfortunately, in your body, these signals aren’t simple, harmless flags or little lights. They are a group of compounds called “inflammatory chemicals” that, in high concentrations, are dangerous for your health.
In fact, having too many inflammatory chemicals in your body for long periods of time is thought to play a serious contributing role in many serious diseases, including:
- heart disease
- strokes and
- metabolic syndrome
Chronic Inflammation and Diseases of Aging
How do chronically high levels of inflammatory chemicals in your body lead to dangerous diseases? Let’s check out the mechanisms one at a time!
Chronic inflammation can mess with your body’s ability to get sugar out of your blood stream.
See, an inflammatory state puts your body on “defense mode”. Your body thinks it’s under attack and that the immune system is working to keep out an invader (even if it’s not).
Just like if you’re worried about being attacked you’re probably not thinking much about what you’re going to eat for lunch, when your body is inflamed it is not very worried about getting sugar from your bloodstream into your cells. In fact, inflammatory alerts sent out by your immune system literally make it harder for sugar to move from your blood into your cells – because defense is the number one priority, not lunch. So, the sugar keeps circulating in your blood.
Long-term high blood sugar levels and difficulty getting sugar into your cells may lead to diabetes.
Heart Disease and Strokes
In the case of heart disease, chronic inflammation can cause plaque to form in your arteries. Plaque is dangerous for your body, so your immune system tries to build a wall or barricade around the plaque, to keep the rest of your body safe.
That may sound good, but those walls it builds are not stable and definitely not meant to be permanent. They make it harder for your blood to get to all the parts of your body and may contribute to high blood pressure.
Additionally, since they’re not permanent structures, bits of the walls can break off and cause heart attacks or strokes as they flow through your blood to sensitive areas like your heart or brain.
Diabetes and heart disease often show up together in something called metabolic syndrome. Having one does not automatically mean you have the other. It definitely does, however, put you at higher risk of developing it.
Unfortunately, chronic inflammation increases the likelihood you’ll develop yet a third risk factor for metabolic syndrome: obesity.
Just like immune cells, fat cells release pro-inflammatory chemicals. So having excess body fat puts you at a higher risk of diseases related to inflammation, like diabetes, heart disease and metabolic syndrome.
That being said, this is not a call to lose all of your body fat. Fat is an essential part of a healthy body, and a healthy diet, and is important for many body functions, including a healthy and working immune system. Too much can be harmful to your health for a number of reasons, but that doesn’t mean you shouldn’t have any.
Risk Does Not Equal Destiny
The tricky thing about these diseases is that chronic inflammation does not always cause them. You may have evidence of chronic inflammation when you’re 90 years old, but never developed any of these conditions. Since we can’t determine who will or won’t end up with these diseases, the best advice we can give is to take care of your body and eliminate any risk factors you can. This might include getting active and losing some weight, making sure you eat foods that have proven anti-inflammatory benefits (such as berries, nuts, leafy greens and spices), and quitting smoking.
Take Home Message
As you can see, your immune system is a big and beautiful thing! Though it starts out kind of wimpy it grows to be a lean, mean, disease-fighting machine, able to detect threats and send in the specific fighters need to win the battle. Over time, however, that machine gets damaged and bogged down with all the protective information it acquires throughout your life, putting you at risk of infections and immune-mediated diseases as you age!