When the Immune System Gets Sick – Part 1

Many germs think our body looks like a pretty great place to call home. The human body provides an ideal environment for various microbes. Most bacteria, we can pleasantly co-exist with. Some are even necessary in order for the human body to remain healthy. Other bacteria and viruses, however, can wreck havoc. Our immune system, then, is the army that keeps these invaders in check.

The immune system is a network of cells, tissues, organs, and proteins that work together to defend the body against “foreign invaders.” Although very complex, it can be thought of as a well-trained army, with different soldiers trained for specific jobs.

Some cells in the immune system are known as “helper cells.” They coordinate the movements of other cells. They receive the alarm (chemical messages indicating an invader) and activate other cells to go to battle. They act as the “general” for the troops.

Cells called “killer cells” embark on search and destroy missions. They take no prisoners! Although they like to punch holes in the walls of bacteria, they are especially tough on “traitors.” They will kill human cells that have become infected with a virus or have turned cancerous. Killer cells stealthily check all of the cells they meet for clues left on the outside of the cell that could indicate a virus or cancer is hiding inside. They have the ability to destroy cancer before it can become a tumor.

“Eater cells” practice a unique form of warfare; they swallow the enemy whole! These cells present parts of the chewed up enemy to the helper cells for identification. Communications are then sent to the rest of the troops regarding the identity of the enemy and the best strategy to fight against this particular foe.

Other immune cells act as war factories. When they receive an alert about an invader, they churn out specific proteins to coat that particular invader. The proteins are like flags or uniforms, in the sense that other parts of the immune system can recognize the microbe as an invader. They also gather the invaders together, holding them hostage until the other troops arrive.

Still, other proteins can trigger inflammation, directly kill intruders, or call killer cells to the area. The success of the immune system is largely due to the elaborate and dynamic communication network between the troops. A multitude of chemicals and receptors are involved in this process.

“Memory cells” have the job of, you guessed it, remembering. Memory cells live a long time and are assigned with remembering every previous enemy. The immune system takes the old adage “Know Your Enemy” very seriously. Memory cells are always on the prowl, looking for invaders that they recognize from a previous battle. If an invader returns a second time, memory cells recognize it quickly, and sound the alarm to roust the troops immediately.

Much of the immune system’s battle can be thought of as a race. Will the invader be able to multiply faster than the immune system can roust the troops?? The memory cells sway the battle in our favor.  When an invader appears a second time, there is already a warning system in place (thanks to memory cells!). The army can then turn the tables on the invader before it has time to gain a foothold and cause symptoms. We would consider this individual to now be “immune” to this invader. On the other hand, when a brand new microbe, such as a cold virus, is encountered, the immune system races to catch up. The week or two of symptoms you feel is part of that process!

Finally, “suppressor cells” call off the troops when the threat is over. This prevents the immune system from damaging healthy human cells or causing autoimmune disease.

I would hate to be a microbe finding myself accidentally up against the human immune system! This army is a vigilant and powerful force, with all sorts of tactics up its sleeve. However, if one part of the army isn’t working right or is absent, a weak spot forms in the defenses. This is known as an immunodeficiency.

Written by Dana Dalbak, PA-C