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Overview of the Immune System

The basic understanding of the immune system is that it has two general sides: innate (or natural) immunity, and adaptive (or acquired) immunity. Our understanding since the 1960s has expanded to see the interplay between these two and three other systems: the microbiome (healthy guts), the interferon system (the all-alert system) and the neural system (nerves). For our purposes here, we’ll concentrate on the first two.

The Innate Immune System

This is also called the natural or non-specific immune system. It has four major components.

  1. Epithelial cells – skin and mucus membranes (think nose, mouth, lungs). The skin is our first line of defense and it does two things. It acts as a barrier, so stuff can’t get in. Healthy skin has densely packed cells that keep things out. It’s also several layers thick and does continuous shedding and renewal. It is also covered with a salty, slightly acidic layer that contains keratin – a protective protein. Mucous is lovely, slimy and sticky, entrapping microbes and unwanted foreigners. More on the goo later.
  2. Phagocytes and Macrophages – these are a type of white blood cell that engulf and digest the little invaders, eating them alive.
  3. Natural Killer (NK) cells – and yup, they go for the heart of the critters like poison.
  4. Finally, the Complement System – this amplifies the inflammatory response, sets the building on fire and at the same time, calls in the army (the adaptive system). If you’ve heard recently of the “cytokine storm”, this isn’t it. The fire from the complement system knows how much to burn and when to self-extinguish. This happens in a healthy immune system.

The Innate system is able to recognize that something foreign is in the body. This is called recognition of the self and non-self. It does this by recognizing certain sugars, fats and proteins on the invader that help them survive, but that are not present in human cells. It doesn’t know the name of the foreigner, it just knows it’s not us.

This system is the first line of defense and is up and running within minutes or hours of first contact. It generally lasts 72 hours as a first line of defense, while the adaptive system builds up the army that will do the specific fighting and killing of the invaders. It is during this time when we have those vague, “flu-like” symptoms, but you’re not feeling truly unwell just yet.

The Adaptive Immune System

Here’s where things get really cool. The adaptive or acquired system, also called the specific system, is built up in this way: through previous exposure to infections and foreign agents. In this way, the body names the enemy and then recognizes it from then on, very specifically.

It is first acquired during breastfeeding while the baby gains protection through mother’s milk. Slowly we expose our children to more germs. First we stop sterilizing everything, then playing on the floor, then outdoors in playgrounds, touching pets and dirt and coming into full contact with the world. All the while their own immune system is beginning to build and strengthen. They begin to recognize the kids in the neighbourhood and their germs too.

What if the germ’s brother comes to call (aka mutation)? No problem. When a mutated version of the same invader comes to call, for instance, a new mutation of one of the flu strains, the body takes much less time to build up the army required to fight, because half of them are already on standby, just shining their boots.

Your lymphatic system is actively involved in immunity. There are two types of lymphocytes that come into play here: the B cells and the T cells.

B cells form the principle defense by splitting into two camps: plasma cells and anti-body secreting cells. In this way they can go to work in the blood stream and in all that glorious goo of the mucosal surfaces. Straight into the fray, they spot the enemy and go in for the kill. This is partly why we create so much phlegm and snot to sneeze, blow and cough out – it expels the enemy where possible instead of dealing with too much battle field cleanup.

T cells are said to be cytotoxic (or poisonous to the cell) and are especially good at spotting and killing viruses. The first thing they do is develop receptors that get up close and personal with the infected cells. Then they figure out and recognize the proteins on the surface of it, which were graciously donated by the virus. Then, the T cells signal the destruction of the infected cell and store the pattern in the Library of Angry Reactions for future use.

We’ve all now seen the handy ball of red fluff with the tiny plungers sticking out of it, that is supposed to be the COVID virus. The B and T cells will recognize the plungers as well as the fluff, and the body’s reaction to it. Both the B and T cells have memory and together create antibodies. These will remain in the body and prowl around, ready to see, recognize and fight the red fluff and plungers and the reaction they bring. If they’re now purple with yellow spots, the body will still recognize the pattern and the reactions, and know how to deal with them. This information has been shared throughout the system and remains for your lifetime.

This system takes a bit of time to get up and running, generally a few days (that 72 hour period) when you’re first sick and maybe feverish. This is because there’s a fair amount of background intelligence work to be done and building up the forces able to deal with it the first time around.

One of the problems with the SARS outbreak was that it proliferated so quickly that it overwhelmed the innate system before the adaptive system could get up and running. This one (COVID) is apparently not so fast working. Highly infectious (a good traveller) but not as obnoxious. The vast majority of those infected recover at home, with no interventions. We are being fear-mongered into thinking it is a killer of mass proportions, and that we are helpless in its path. Not so.

Trust in your body. Vaccinate, or don’t, but know that your body is a marvel of first and second defense. It is a miracle of healing for the whole of our lives. Constantly in search of homeostasis, a healthy immune system adapts to everything that is thrown at it. Once it has recognized and built its defenses against something, the memory and the fighting ability are there for life. As we age and become weaker, the fight goes out of us a bit. But the memory is long.

Healing is our superpower.

Reference: Pathophysiology by Carol Porth

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3 thoughts on “Overview of the Immune System”

  1. I really found this very interesting as I am battling ovarian cancer at age 74 which I am told us very aggressive. Before my 74th birthday in May, i did not even have a tooth ache, no medical conditions like diabetes, nothing! I do not even have a cavity in my teerh. I went in for a simple hysterectomy and woke up to find out I have stage 3 ovarian cancer and they gave me a colostomy. Well, I am determined to fight this and come out a winner. If you have any good advice, I would love to hear it. They do a blood test every week and my oncologist told me that my immune, kidney and liver are in excellant condition and I would like to keep it that way.

  2. Jason Vander Meulen

    This was a fascinating read! I’m always looking for new ways to explain how first contact was so devastating for the indigenous populations of Turtle Island. I think I’ll use this to illustrate the mechanics of sicknesses like small pox.

    Thanks for sharing.

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