How Many Parts of Your Immune System Can You Name?

by
Dr. Ariel Thorpe

The immune system is our defense system against any potentially harmful invaders. While our immune system has always been essential to our survival, it is receiving special attention right now. So, what better time to learn some specifics about what this system is and what it does for us?

The immune system consists of two parts: the innate immune system and the adaptive immune system. Your innate immune system is the general, big-picture defense that everyone was born with. Its purpose is to defend against foreign bodies, injuries, and pathogens. Its job is to:

  1. Kill bacteria
  2. Provide protection on the outside of your body (ie. Your skin)
  3. Provide protection on the inside of your body (ie. Mucous membranes like your intestinal walls, gums, lung membranes, etc.)
  4. Scavenge the body for invaders

Your adaptive immune system is highly specialized to fight specific pathogens or your own cells if they have become harmful to you. This system gains its power over time as you become exposed to various viruses, bacteria, and fungus over the course of your life. It consists of:

  1. B lymphocytes (aka B cells), which are defense cells in the blood
  2. T lymphocytes (aka T cells), which are defense cells in the tissues
  3. Antibodies

If you like sports metaphors, imagine playing an impromptu rugby game. You show up to the pitch, you’re playing defense and you know the general objective: stop the other team from getting the ball. That’s the innate immune system. Now imagine a professional rugby team; they have studied their opponents’ strategies and previous games. They know exactly how each player will show up to play and will adapt their own strategy for that team. That’s the adaptive immune system.

Innate Immune System

It may come as a surprise that your skin and mucous membranes are part of your immune system. But this is the innate immune system’s essential first line of defense. Imagine how many germs would get into our bodies if we didn’t have skin! And this is why it is important to take care of our skin and adequately clean and dress wounds to prevent infection. Should something enter via an orifice, we have our mucous membranes as the second line of defense. Although those tissues are wet and somewhat absorbent, they are selective about what they want to let enter the body. (Think about it like this: the “inside” of the body is only the area within our skin and mucous membranes. That means, the entire digestive tract from mouth to throat to stomach to intestines to anus is all  “outside” the body. Our food isn’t “inside” of us until it is absorbed through the walls of our digestive tract.)

In addition to these physical barriers, we also have various chemicals along these surfaces to keep microbes from getting in. And our bodies use movement to keep the baddies from hanging around. The cilia (small hair-like structures) in the lungs help brush bacteria out, which is why smoking is especially bad for our immune system, as it destroys those cells. Our bowels contract to move waste along so bacteria goes out rather than in. Our tears, sweat, and urine also help expel unwanted guests. (So crying, working out, and drinking plenty of water can help keep your immune defenses strong.)

Scavenger cells are a specific white blood cell that act like garbage disposals. They engulf microbes and break them down. The scavenger cell then takes the broken down bits and holds them on their surface to “show” to your adaptive immune system cells. Your adaptive immune system cells (B and T cells) then learn to recognize those little pieces so they can fight them off later.

Natural killer cells are another white blood cell whose job is to recognize and destroy cells that have been infected by a virus or have become tumorous. These cells are essential for fighting off viral infections and cancer.

When our immune system kills off an invader, it ends up with waste in the form of pus. So, next time you see pus - whether it is a pimple or a wound - you’re literally looking at your immune system’s hard work!

Adaptive Immune System

Our bodies are so brilliant that, when necessary, they can call in the big guns when the innate immune system needs some help. If our innate immune cells are the foot soldiers of our immune system, our adaptive immune cells are the special forces. This is the part of our immune system that gives us the ability to confer long-term or life-long immunity. While not every viral or bacterial infection can confer life-long immunity, having a strong adaptive immune system is vital.

Our bones - specifically in the bone marrow - make our blood cells including our T cells and B cells. The T cells are named for their site of maturation, the thymus gland. There are three types of T cells:

  1. T helper cells are like little megaphones that call out to other immune cells to start the adaptive immune response using chemical messages.
  2. Cytotoxic T cells identify and destroy cells that have been compromised by a virus or become tumorous.
  3. Memory T cells remember which invaders have entered your body before so that you can have a quick response to future exposure to the same microbe.

B cells are named for the bone marrow that produced them. B cells ultimately make antibodies specific to the invading microbe. Some B cells become memory cells for future exposure.

This leads us to the final part of the adaptive immune system: antibodies. Antibodies are extremely specific and match to specific invaders called antigens. Sometimes this relationship is referred to as “lock and key” because only one antibody and one antigen will fit one another.

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