Do you remember the last time you were sick? Maybe you had a cold, the flu, or a stomach ache. You probably felt very sick, but after few days you felt healthy again, thanks to your immune system! Your immune system gets rid of things that make you sick!
There are two types of germs that make you sick: bacteria and viruses. Bacteria and viruses are usually to blame for bringing on nasty colds, fevers and fatigue (tiredness), and many serious infections. There are other life forms that can make you sick as well, such as parasites and fungi, and also non-living things like chemical toxins. Some common germs are the influenza virus that causes the flu, and the bacterium streptococcus pneumoniae which causes pneumonia.
Viruses and bacteria can both make you sick, but they are very different!
Bacteria are single-celled organisms. That means that they are living things that are made of only one cell. Bacteria can live on their own, or they can live inside another organism. When you get a bacterial infection, the doctor will give you antibiotics. Antibiotics kill bacteria. But, not all bacteria make you sick. Some are actually very helpful!
Viruses are much smaller than bacteria. They are so small they can't live on their own. They have to infect the cells of another organism to live. This means that they get inside of a cell and kill it. Antibiotics do not kill viruses, so taking antibiotics when you have a viral infection won't help make you better.
Not all diseases are caused by germs. Some diseases are caused by mistakes in your DNA. These kinds of diseases are called genetic diseases.
How do you get sick?
Germs can infect you in many different ways. Sneezing, coughing, kissing, or touching contaminated areas can spread infections like the common cold. Bacteria can get into your body through a cut, through food, or through your eyes. This is why it is so important to wash your hands!
There are many ways germs spread from person to person, and each germ is different. But, you can help to stop them from spreading by always covering your nose and mouth when you cough or sneeze and by washing your hands.
If it is so easy to get germs into the body, why aren't we sick all the time? Luckily, our immune system is working around the clock to fight off infections.
What is the immune system?
The immune system is a network of cells, organs and vessels that work together to protect nearly every area of our body. Each type of immune cell has a special job. Some kill infected cells, some carry messages, some make antibodies, and others get rid of dead cells. The organs in our immune system also have special functions. The thymus, spleen, and tonsils are important immune organs.
How does each cell know what job to do? Are they just born that way? And how do they differentiate between “good” and “bad” cells? How do they know not to attack your own healthy cells?
Distinguishing self from non-self
The most important role of the immune system is to tell the difference between things that are healthy and belong to your body, and things that don’t! Something that belongs to the body is called “self.” Something that doesn’t belong in your body is “non-self.” Think of the wide variety of different tissues and cells that can be found in your body: hair cells, teeth cells, bone cells, blood cells, and even some friendly bacteria that live in our intestine to help us eat! Your immune system has to be very smart to be able to tell the difference!
If we understand how the immune system works, we can cure infections and diseases. But, if you are just beginning to explore the immune system, the most important idea to remember is that our immune system has “learned to learn.” Through millions of years of evolution, our immune system has acquired the ability to learn and remember information about the billions of different cells and substances it comes into contact with every day. Without the ability to learn and remember, you’d keep getting sick from the same thing over and over!
Do you remember the last time you were sick? Chances are you remember having had a head cold or the flu, or maybe even a stomach virus. You might have thought that you were never going to recover, but in a few days you were feeling like yourself again thanks to your immune system!
Pathogens - What makes you sick?
Bacteria and viruses are usually to blame for bringing on nasty colds, fevers and fatigue, and many serious infections. There are other life forms that can make you sick as well, such as parasites and fungi, and also non-living things like chemical toxins. Any microorganism that causes infection is called a pathogen. Some common pathogens are the influenza virus that causes the flu, and the bacterium streptococcus pneumoniae which causes pneumonia.
Transmission - How do you get sick?
Pathogens can infect you in many different ways. Sneezing, coughing, kissing, or touching contaminated areas can spread infection. This is how the common cold is mainly spread. Many bacterial diseases can come from leaving open wounds untreated, eating contaminated food, or touching a contaminated surface and then your mouth or eyes. Yet more chronic diseases can spread through transferring blood or sexual contact, like the HIV virus. There are many ways pathogens spread from person to person, and each pathogen is different. But, you can help to stop them from spreading by always covering your nose and mouth when you cough or sneeze and by washing your hands.
With so many points of entry and so many dangerous microbes out there, it seems that we should be sick all the time. Luckily, our immune system is working ‘round the clock to fend off infections from outside particles and clean the body of dead or old cells.
What is the immune system?
The immune system is not located in a specific organ. It’s easiest to think of our bodies’ immune system as a complex network of different types of cells, like B and T cells, and tissues, like the lymphatic system and the thymus, that work together to protect nearly every area of our body. Each type of cell is prepared to perform certain functions, such as killing damaged or infected cells, carrying messages, making antibodies, or carrying away debris.
You might ask, how does each cell know what job to do? Are they just born that way? And how do they differentiate between “good” and “bad” cells, knowing not to attack your own healthy cells?
Distinguishing self from non-self
In fact, this is the most important function of the immune system: to distinguish what cells and substances belong to your body and are healthy, and which aren’t! What belongs to the body is referred to as “self,” and something that doesn’t belong as “non-self.” Think of the wide variety of different tissues and cells that can be found in your body: hair cells, teeth cells, bone cells, blood cells, and even some friendly bacteria that live in our intestine to help us eat! Your immune system has to be very smart to be able to discern such a variety of things!
Understanding how the immune system works could reveal the key to curing many infections and diseases. But, if you are just beginning to explore the many functions of the immune system, the most important idea to keep in mind is that our immune system has “learned to learn.” In other words, through millions of years of evolution, our immune system has acquired the ability to learn and remember information about the billions of different cells and substances it comes into contact with every day. Without the ability to learn and remember, you’d keep getting sick from the same thing over and over!
