The Body's Defense

whats the point?

By the end of this lesson, students will get a clear idea of how our immune systems function, the different ways they protect us, and what can go wrong if the immune system doesn't do its job.

You’ve done some impressive detective work figuring out the different microbes that might have been causing the Thompson family and their neighbors to feel under the weather.

Now, we will focus on how our bodies try to fight off these tiny invaders.

In this lesson, we'll explore the body’s defense systems—how our immune system acts like a superhero team, always on guard to protect us.

We'll also look at what happens when these defenses aren’t enough, which can lead to what’s called homeostasis failure, where the body can’t keep its internal environment stable and healthy.

To try to help the Thompson family’s situation, we will start to connect the dots between the pathogens you've researched and the immune responses they trigger. We will continue to build on what you’ve learned about pathogens by showing you exactly how the body tries to keep them at bay.

Get ready to enhance your knowledge of epidemiology and learn about the battles happening inside our bodies every day and how understanding these can help us better manage and prevent illnesses.

Your immune system is like self defense

The body's defense is better known as the immune or lymphatic system. The immune system is a network of cells, tissues, and organs that work together to defend the body against attacks by invaders. These invaders are primarily microbes or tiny organisms such as bacteria, parasites, and fungi that can cause infections. The human body has ideal conditions for many microbes. The immune system's job is to keep them out or, if they make their way inside the body, to seek out and destroy them.

Immunity is an organism's ability to resist infection or disease and can be classified as active or passive.

Active immunity develops when the body produces antibodies in response to an antigen, such as from vaccines or natural infections.
Passive immunity is acquired when antibodies are transferred from another source, like from mother to child through the placenta or breast milk.

Remember that Pathogen Gang?

A pathogen is any microorganism that causes disease in its host. It can be transmitted in two main ways: direct and indirect transmission. We will discuss these types of transmission in more depth later in this module.

The Three Levels of Defense

The Immune System Super Hero Team

The immune system stockpiles a huge arsenal of cells, including lymphocytes (B and T), phagocytes, and granulocytes.

You can think of all these cells working together as a team to fight off the pathogen gang!

Let's meet these heroes and learn about their superpowers.

To Recap:

B lymphocytes' major function is to produce antibodies in response to foreign proteins from bacteria, viruses, and tumor cells.
- - Antibodies = large Y-shaped specialized proteins that specifically recognize and bind to one particular protein.
  - Antigen = a protein on the surface of a cell (such as bacteria or viruses) that prompts the immune system to produce antibodies against it.

The dynamics between antigens and antibodies are central to the immune response. Antibody production and binding to an antigen, often is critical as a means of signaling other cells to engulf, kill or remove that substance from the body.

Phagocytes are large white cells that swallow and digest microbes and other foreign particles. Some immune cells take on all intruders, whereas others are trained on highly specific targets. To work effectively, most immune cells need the cooperation of their comrades. Sometimes, immune cells communicate by direct physical contact, and sometimes, they communicate by releasing chemical messengers.
Macrophages play many roles. As scavengers, they rid the body of worn-out cells and other debris and produce a variety of chemical signals vital to the immune response.
Granulocytes are another kind of immune cell. They contain granules filled with chemicals that allow the granulocytes to destroy microorganisms. Some substances, such as histamine, also contribute to inflammation and allergy.
Helper T cells, or Th cells, communicate immune responses with other cells. Some stimulate nearby B cells to produce antibodies, others call in microbe-gobbling cells called phagocytes, and still others activate other T cells.

The immune system stores just a few of each kind of cell needed to recognize millions of possible enemies. When an antigen first appears, the few immune cells that can respond to it multiply into a full-scale army of cells. After their job is done, the immune cells fade away, leaving sentries behind to watch for future attacks.

Now, Back to the Thompson Family.
Where do you think their immune systems failed?

That's the point

The immune system is a complex network that defends the body against pathogens like bacteria and viruses. It recognizes and remembers specific pathogens, utilizing white blood cells and antibodies to fight threats. The immune system has three lines of defense that work together to protect the body. When the immune system fails, the body becomes susceptible to infections and diseases.

►Next Up: This next lesson will deepen our grasp of infectious disease mechanics and emphasize the urgency of finding innovative ways to counteract antibiotic resistance, an increasingly critical challenge in global health. We are getting closer and closer to figuring out what is making the Thompsons and their community sick, and hopefully, we can treat it soon!

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