How Do We Get Sick?

Our bodies are constantly warding off bacteria and infections to keep us from getting sick; they are laboring on our behalf every single minute, every single second even!

Despite our bodies’ valiant efforts, sometimes we still get sick. How does it happen? What’s actually going on inside?

First things first. Sickness is a result of a bacterial, fungal, or viral invader called a pathogen, which grows and multiplies in our body, taking over the body’s resources to further its own proliferation. (Some bacteria even release toxins into our bodies in order to get a bigger advantage.)

In order to prevent sickness from getting established our body has a defense system known as the immune system, which is designed to protect us from invaders. Think of the immune system as an “intelligent barrier,” dealing with all the evil, harmful invaders of the world! Dramatic, yes! But our bodies really do a remarkable job of protecting us from the bacteria, viruses, and fungi, as well as toxins and pollutants found in our environment.

The immune system is actually composed of two branches: innate immunity and acquired immunity. These are fancy titles that describe a general defense system (innate immunity) which defends against a broad range of intruders, and a specific defense system (acquired immunity) which defends against a previously encountered invader.

Innate immunity then, is a general line of defense that catches all sorts of bugs based on common features. It is a broad safety net that catches most invaders before they have a chance to do damage. Pathogen Associated Molecular Patterns or PAMPs is the technical term that immunologists use for identifying common features of invaders. The bacterial “tail” or flagellum is one such feature that alerts the immune system to the presence of an intruder.

Components of innate immunity include:

• Skin, mucous, hair, stomach (digestion)–any physical barrier between our bodies and the external world. If the bug can’t get in, it can’t make us sick.

• Surveillance of common ‘bug’ components (PAMPs – see above), like the flagellum, bacterial cell wall, toxins, etc. Once the bug is in, it can be recognized and removed.

• Scavenging/cleaning cells (macrophages, eosinophils, neutrophils, all falling under into the category of phagocytes–cells that engulf intruders in order to sequester and kill them.

• The complement system–a complex of proteins that bind to intruders making them easier to dispose of by phagocytes.

So a “bug” needs to first get past the surveillance system of innate immunity in order to inflict sickness on our body! This might seem impossible considering the array of defenses in this first “tier,” but unfortunately, it does happen. The system is weakened by a number of factors including fatigue, poor diet, dehydration, stress, sugar, and poor hygiene. Not to mention the pathogens which evade innate immunity because they don’t possess the features that will give them away–having evolved to sneak past our surveillance system!

Now what? The body must have something up its sleeve or we would be sick all of the time! Well, this is where the second branch of the immune system comes in. What is not picked up by innate immunity can be recognized by acquired immunity.

Acquired immunity is a more specific recognition system and, as the name suggests, is able to adapt to what we are exposed to. This is how acquired immunity works:

1. A pathogen enters our body.

2. Our body recognizes the foreign substance with a diverse array of receptors called antibodies.

3. The specific antibody is multiplied and the intruder is overwhelmed.

But what exactly is an antibody? An antibody is a receptor created by the body to recognize “non-self,” or more simply, anything foreign. Antibodies are composed of two heavy chains and two light chains that come together to form a “Y”-shaped protein. They are created to have an enormous amount of diversity at the receptor end.

Indeed, the diversity of what antibodies can recognize is staggering. Here’s how they work: initially the body creates the variability in small numbers. Then each antibody is checked against “self” proteins (proteins that our own body makes). This “check” ensures that antibodies don’t react with the body’s own proteins and begin fighting itself. (Unfortunately, this does happen–called “autoimmune” diseases. Some examples include: Lupus, MS, Grave’s disease, and Rheumatoid arthritis.)

The antibodies detect a bacterium in two ways:

1. Direct binding of the antibody to the intruder, or

2. Binding of a broken down component of the bug via an Antigen Presenting Cell (APC). APCs are phagocytes (see above) that engulf and digest the bug.

Once an antibody binds to an antigen the alarm bells go off and production of that specific antibody goes into overdrive.

The only downside of this operation is time; it takes time and a lot of energy to produce a host of antibodies. Often we get sick because a bug establishes itself before the body can respond. But when the antibodies are ready (about 3-5 days for an initial exposure), they overpower the enemy and the body begins the “clean-up” and healing process.

But what happens if you have already been exposed to a bug?

This is the cool part. If you have been exposed to a sickness that was fought with acquired immunity then the antibodies are already at reasonable levels in your blood stream. As such, the response to a secondary infection has a rapid response rate of 24 hours, as compared to the 3-5 day timeline for the initial encounter. And thus acquired or adaptive immunity get its name…we develop resistance to bugs we’ve been exposed to.

Hence all the nervousness and hype about shots when traveling to exotic places; we don’t have the same immune system as the resident population. One can get really sick from a bug to which the locals are totally immune. Interestingly, our immune systems are unique to each one of us and tell our individual “infection” stories, from birth to present!

But can we create immunity to specific bugs before we encounter them? Of course! This process is what we call vaccination. By exposing the body to an attenuated (less harmful) bug, one can develop antibodies that will give immunity to the bug itself.

Vaccines are also created with dead bugs or parts of the intruder or from the toxins they secrete. Once antibodies are created and amplified in response to these methods, the body is primed to defend itself. One caveat: if you are immunized against a specific type of flu virus and another strain comes around, you are likely to get sick as antibodies are very specific.

Bottom line. Sickness is caused by an intruder which evades our defense system and is able to take advantage of our resources.

But can we prevent sickness? Yes! We’ve alluded to factors that weaken our immune system, but check out our specific article on Glutathione, an essential protein that the body creates in order to enable health!