Immunology. Say it with me: Imm-yuh-nah-lah-gee. Excellent! Now, let’s discuss what this weird-looking word means, and why it is important to us.

Immunology literally means the study (‘-ology’) of the immune system (‘immuno-‘). Wherever you see that ‘-ology’ suffix, understand that you’re dealing with the study of something.

When it comes to immunology, there are many different branches within the field of study, including how our bodies respond to:

1. Bacteria

2. Viruses

3. Fungi

4. Parasites

5. Allergens (i.e. pollen)

6. Ourselves (i.e. autoimmunity/cancer)

When our bodies mount an immunological (meaning: related to immunology; ‘-ical’ = ‘related to’) response, that event is called ‘inflammation’. This occurs when our immune system encounters any of the entities listed above, and it also occurs when we experience an injury such as scraping our knee, tearing a ligament or breaking a bone. We also have to consider that how our human bodies respond during inflammation differs from other living organisms.

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For instance, there are some strains of virus (influenza comes to mind) that predominately impact birds but not humans, and vice-versa; refer to the figure below. In a minority of cases, a bird-specific virus can undergo a change (aka a mutation) and be able to transmit from bird to human.

Slightly different strains of the same virus can produce completely different symptoms in their respective hosts. Here, Strain A of this virus makes humans sick, but not birds. Conversely, Strain B of that virus exhibits the opposite effect.

In certain contexts, some organisms and animals can display very similar immune system responses as humans (i.e. pigs, fruit flies, mice, non-human primates), and this explains why they may be used in research studies relevant to humans. However, the subtle differences in those responses can sometimes lead to very different outcomes when the results of those studies are applied to human circumstances, in the form of treatments and therapies.

When a disease-causing agent enters the body and encounters that body’s immune system, that is considered a ‘host-pathogen’ interaction. Animal and insect models of all types can be used in research to demonstrate these interactions within humans, including mouse, non-human primate, and fruit fly models.

The most ideal outcome of these treatments and therapies is a ‘cure’, which helps bring the body back to its normal state (we scientists call this state, ‘homeostasis’) and we feel good again, because we have gotten rid of the problem!

So no, science is not always straight forward, and yes, it can get complicated.

Sorry.

Now that we have a better understanding of what immunology is, let’s talk about what our immune system is composed of.

Think of the immune system as a unique, internal military of our bodies, with different divisions and subgroups represented by different types of immune cells. All of which, are conducting different lines of work to protect us and keep us healthy.

There are two over-arching branches of the immune system, which include:

1. The innate immune system

2. The adaptive immune system

Our hair and skin are the greatest protection against the forces outside of our bodies, but when those layers are compromised and something gets in, the innate immune system serves as our first line of defense. This is generally comprised of the following cell types:

1. Neutrophils

2. Monocytes

3. Macrophages

4. Dendritic Cells

5. Eosinophils

6. Natural Killer Cells

7. Epithelial Cells

8. Mast Cells

9. Basophils

The primary role of this innate immunity group is to recognize and neutralize whatever is causing the inflammation, as quickly as possible, while minimizing any possible collateral damage to the immediate environment. Some cells seek-out the actual agent that stimulated the immune response in order to engulf and digest it, while other cells aim to remove or destroy host cells (any cell that originates from our body) that are infected or compromised in any way.

The other branch of the immune system is the adaptive immune system, which behaves as the special armed forces of the immune system. The innate immune system functions to attempt to clear whatever is causing inflammation the best it can, but when clearance can’t be achieved it aims to contain the inflammatory agent until the adaptive immune system kicks in.

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How long does this process of sending in the cavalry take? Oh, maybe 4-7 days. That’s why when you get a cold or a flu, you typically feel the scratchy throat and stuffy head symptoms for about a week – sometimes longer.

Hold up. I know what you want to ask. “Why so long, though?”

Well, to keep it simple I’ll provide you with the following analogy:

Imagine you walk into a store to find a formal suit or dress for an event. You have suits/dresses that are pre-made and ready to buy off the rack. The fit may not be exact, but it’s close enough to get the job done, and the task can be completed in a day or so. This would be your innate immune system.

However, if you want to fully customize your suit/dress, you have to pick out the material you want and have measurements taken so that it hugs your contours and fits you like a glove. This process takes time and between picking materials, taking measurements, and having the tailor work his/her magic in putting the garment together, this can take months!

But, the end result is a high quality garment, made to precisely fit you in that moment in time. This would be your adaptive immune system.

So, with that story in mind, you may now better understand why there are some pathogens that require a little extra time for our defenses to develop a precision attack plan, specifically for that entity. Unfortunately, there are some complex pathogens that our bodies are unable to clear on their own, and we require the assistance of supplementary treatments to clear them, or to at least stop them from causing further harm.

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As you can see, a lot goes on in our bodies when it comes to the function of our immune system, and it is always on watch 24/7. Our bodies are so good at what they do, you never even notice they’re working, most of the time. This only scratches the surface of immunology but as you will see in future parts of this series, there are countless details considered to protect our health. Most of the time you never know it’s happening, except, for example, when an infection takes hold in the form of a bad cold and you experience symptoms.

I hope you walked away with a better understanding of immunology (imm-yuh-nah-lah-gee 😉 ) after reading this, and check back for the next part of our immunology series. There is so much more to learn!

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