The immune system does so much more than fight off colds, it's working 24/7 to protect you from infections, repair damage, and keep your body in balance!

But how does it actually work? And why does it sometimes mess up and cause allergies or autoimmune diseases?

In this post, we're going to break down the basics of the immune system in plain language, no textbooks required! Whether you're a student, someone managing allergies, or just curious about how your body works, this guide is for you :)

What Is the Immune System, Anyway?

The immune system is basically your body's defense system, it is a network of organs, proteins, white blood cells (WBCs or leukocytes), and chemicals. All these parts work together to protect you from germs and other invaders that can be a danger to your health. Not only does the immune system help prevent sickness, it also helps your body heal from any wounds or fight infections (Cleveland Clinic, 2023). 

The Two Main Parts:

• Innate Immune System:

  • • Fast & general response

    • Responds in the same way to all foreign substances and germs

    • Includes skin, mucus, hair, and other epithelial barriers

      • • Epithelial: "Refers to the cells that line the internal and external surfaces of the body." (NIH, 2023)

• Adaptive Immune System:

  • • Slow & targeted response

    • Learns over time

    • Uses lymphocytes (T cells & B cells)

    • Remembers any invaders for the future (this is the basis for vaccines!)

Meet the Key Players

How the Body Responds to Invaders

1. A pathogen enters

2. The Innate immune system responds first

3. If needed, adaptive system will kick in.

4. Antibodies and memory cells are created

Depending on the circumstances, the corresponding system will take charge. For example, somebody who recovers from measles will be protected against measles for the rest of their life thanks to their adaptive immune system. 

On the other hand, the innate immune system will kick in when, for example, somebody gets a cut. Cells of the innate immune system located in the affected tissue, such as mast cells and macrophages, detect the damage and the presence of these foreign invaders that came in through the cut. These cells release chemicals, including histamine, that cause nearby blood vessels to widen and become more permeable (causing the characteristic signs of inflammation!). This increased blood flow brings more immune cells, particularly neutrophils, to the wound site. Neutrophils are the "first responders" of the innate immune system, and they begin to engulf and destroy any bacteria present through a process called phagocytosis. Neutrophils and other phagocytes continue to work to eliminate the pathogens and clear debris from the wound. They release antimicrobial substances and also produce toxins to kill bacteria. Once the immediate threat is contained, the inflammatory response decreases, and macrophages shift from  pro-inflammatory to a reparative state, promoting tissue regeneration. Now, even though the innate immune system went through all that, it will not remember the specific bacteria that entered through the cut.

What Happens When Things Go Wrong?

Your immune system is smart. Most of the time, it fights off harmful invaders, heals wounds, and keeps you feeling well. But sometimes... it gets confused, goes into overdrive, or just doesn't work the way it should. Thats when things can go wrong.

Up next are three big ways that the immune system can misfire, and what that means for your health:

Allergies: When Your Body Overreacts

Allergies happen when your immune system treats something harmless (e.g pollen, peanuts, pet dander, etc) like a dangerous threat.

Your body releases chemicals like histamine, which cause itching, sneezing, swelling, or even serious reactions like anaphylaxis.

It's not the pollen thats the problem, rather your immune system's response to it!

Autoimmune Diseases: Fighting the Wrong Target

Autoimmunity is when your imune system attacks your own cells by mistake. It can't tell the difference between "you" and an invader. The CDC explains that autoimmunity occurs when the body can't tell the difference between healthy cels and harmful ones.

Some examples include:

• Type 1 Diabetes - the immune system attacks insulin-producing cells in the pancreas.

• Lupus - affects joints, skin, and organs

• Rheumatoid arthritis - attacks the joints

Immunodeficiency: When the System is Weakened

Sometimes the immune system is too weak to protect you. This can be inherited (aka, you're born with it) or acquired later in life.

A weakened immune system makes it harder for your body to fight infections, even common ones.

Examples include:

• Primary immunodeficiencies - rare genetic conditions like SCID

• HIV/AIDS - a virus that damages the immune system over time

• Chemotherapy - temporarily weakens the immune system

Why this matters:

When your immune system doesn't work the way it's supposed to, it can lead to chronic illness, frequent infections, or even life-threatening reactions. But learning how it works and what can go wrong is the first step towards understanding and managing it. 

This is why immunology is so important! It helps scientists, doctos, and patients work together to treat, prevent, and hopefully one day find a cure for these conditions.

Thanks for stopping by and learning with me! I hope ImmunoWise helped you feel a little more informed and a lot more curious. The immune system is complex, but understanding it doesn't have to be. I'm just getting started, and I'm glad you're here for the journey.

Don't forget to wash your hands,

-Dom :)