Your immune system is an amazingly elaborate system designed to protect you from foreign invaders. When bacteria, parasites, fungi, viruses and other pathogenic microbes enter your body — via your nose, mouth or eyes, in food, water, or air, or through sores or cracks on your skin — your immune system launches its attack.
How Does Your Immune System Work?
Your immune system is made up of millions of cells, tissues and organs that interact to make a complex, protective defense system. Your first line of defense is your skin, which acts as a barrier against invading pathogens and also secretes an antibacterial substance to kill mold and bacteria. Generally speaking, bacteria and viruses cannot permeate your skin unless you have a cut or abrasion that allows them an entry point.
If an invader tries to enter through your nose or eyes, your tears and mucus in your nose and lungs contain lysozyme, an enzyme that helps break down bacteria. You may also sneeze or cough if a microbe enters your nose or throat, which may expel the pathogen outright.
If a bug enters your stomach, stomach acid will destroy many varieties. And if it manages to survive all of these primary defense mechanisms, it will still have to make it past tightly packed epithelial cells and mucus, which make it difficult for invaders to get into deeper cell layers.
When bacteria, viruses or parasites get deeper within your body, this is when your immune system launches a full-fledged attack.
A Fine-Tuned Pathogen-Busting Machine Infectious diseases, which include everything from colds and flus to AIDS, are the most common cause of illness in humans. Typically these result when a germ makes it past your body’s first broad defenses, and then takes up residence deeper within your cells, bloodstream or tissues. But if your immune system is functioning properly, the invader will not be allowed to stay without a fight.
As the National Institute of Allergy and Infectious Diseases states:
“The immune system is amazingly complex. It can recognize and remember millions of different enemies, and it can produce secretions (release of fluids) and cells to match up with and wipe out nearly all of them.
The secret to its success is an elaborate and dynamic communications network. Millions and millions of cells, organized into sets and subsets, gather like clouds of bees swarming around a hive and pass information back and forth in response to an infection.
Once immune cells receive the alarm, they become activated and begin to produce powerful chemicals. These substances allow the cells to regulate their own growth and behavior, enlist other immune cells, and direct the new recruits to trouble spots.”
For instance, antibodies may attach to a bacteria and direct special cells called phagocytes to destroy it. They can also attach to viruses and kill them before they’re able to enter your cells, and if a virus enters your cells, the cell will “flag” itself as infected so another component of your immune system, your T cells, can then destroy it.
In the case of certain parasites, especially those that are larger than bacteria and viruses, immune cells will surround the invader and release chemicals in an attempt to kill it.
As you can see, this system requires a coordinated attack that is put together by many different immune system components. The main components of your immune system include:
- Thymus, which produces immune system T cells.
- Spleen, which helps filter your blood and detect foreign cells.
- Lymph system, which helps to detect, filter and remove bacteria from inter-cell fluid. Bacteria and the cells fighting it collect in your lymph nodes during an infection, causing them to swell, which is why your physician may check for “swollen lymph nodes” if you’re feeling sick.
- Bone marrow, which produces lymphocytes — white blood cells that play a key role in your immune response.
- White blood cells, which are one of the most important parts of your immune system. More than a dozen different types of white blood cells work to help destroy foreign invaders.
- Antibodies, proteins produced by white blood cells that attach to specific pathogens then disarm them or assist in their destruction or removal.
- Complement system, proteins that float in your blood and assist antibodies in their attack and removal of pathogens.
- Certain hormones are also generated by your immune system. Some of them may help your body to produce a fever, which can help to kill bacteria and viruses.