Kelly has taught High School Science and Applied Communications. She holds an Education Specialist Degree in Ed. Leadership.
The immune system is the body's defense mechanism that protects the body from intruders. It is made up of a network of cells, tissues, and organs. The word 'immunity' in this case means protection against disease. That is exactly what the immune system is supposed to give you.
There are many different types of invaders that can harm the body. Most of the invaders are little microbes, such as bacteria, parasites, fungus, and viruses. All of these can cause infections inside the body. The more technical name for the invaders - or at least the ones that cause the immune system to move into action - is antigens.
The immune system is extraordinary. It will attack these annoying little antigens by locking them into their sights, sending for back up, and chewing them up until they are gone. The immune system is so smart that it can recognize a 'self' cell and a 'non-self' cell. Basically, the immune system knows which cells belong to you ('self cells') and which ones do not ('non-self cells'). Antigens are the non-self cells that trigger the immune system into action. These antigens can be viruses, even a molecule of a virus, or tissues and cells from another person. This reaction is why a person may reject an organ transplant.
When all is working properly, the immune system leaves the healthy cells and tissues in the body alone. When the immune system is not working well, it may attack the self cells; however, when the immune system is not working properly, it can cause harm to the healthy parts, causing disorders such as allergic diseases, arthritis, and certain forms of diabetes. This malfunctioning is known as autoimmune disease.
Sometimes, the antigens are actually harmless. This is the case with stuff like ragweed or pollen. Both are harmless to the body; however, they may trigger the immune system into action. These types of harmless antigens are known as allergens.
The immune system is a huge communications network made up of cells, tissues, and organs that are placed all throughout the body. Such placement is beneficial because it cuts down on travel time. Let's look more closely at some of these special components and their roles in protecting the body.
There are millions of cells throughout the body that are just waiting to jump on these antigens and destroy them. These cells are called leukocytes, or white blood cells. Leukocytes are divided into two categories: phagocytes and lymphocytes.
 |
Phagocytes are the cells that destroy the antigens. They are the ones that chew up the antigens until they are gone. The most common type of phagocytes is the neutrophil, which fights bacteria. A doctor can draw blood and, if there is a high number of neutriphil cells, determine that the body probably has a bacterial infection.
Lymphocytes are the immune system's intelligence gathering cells and front line of defense. There are two types of lymphocytes. B lymphocytes, or B cells, travel around the body and tag the antigens. They send signals to the T lymphocytes, or T cells. The T cells then begin to destroy the antigens the B cells identified. The T cells get back-up from the phagocytes, which finish off the antigens.
The organs of the immune system are called lymphoid organs. This is because they are home to the lymphocytes, or white blood cells. Bone marrow is soft tissue that is in the hollow center of the bones. It is the ultimate source of all blood cells, including the lymphocytes. The spleen is a gathering place for all of the cells.
The lymph nodes are found throughout the body near or inside the lymphatic vessels. They are meeting places for immune cells. The immune cells, antigens, and many of the other things listed in this lesson so far travel throughout the body via lymphatic vessels. Lymphatic vessels are very similar to the veins and arteries that line the insides of our bodies.
The thymus is where the T cells go to grow up. Once they mature, they move to other tissues throughout the body. It is located right behind the breast bone, which is a nice central location for the cells to be.
 |
Invaders, antigens, attack the body. This triggers an alarm for the B cells to produce special proteins known as antibodies . The B cell will lock the antibody onto the invading antigen. The antibodies are markers that signal T cells and eventually phagocytes to attack. The antibodies will remain in the body for good. This is why immunizations work. They have just enough of the antigen in them so you do not get sick, but your immune system creates the antibodies that will destroy it if the antigen were to return.
The immune system is the body's defense against invaders that could cause infection. Parts of the immune system are found all over the body. They each have their own roles and functions. All of the parts work together to form a huge communication network that gets rid of antigens, or invaders, that could cause the body harm.
When this lesson is over, you should feel satisfied with your ability to:
Medical Disclaimer: The information on this site is for your information only and is not a substitute for professional medical advice.
To unlock this lesson you must be a Study.com Member.
Create your account
Already a member? Log In
BackAlready registered? Log in here for access
Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.
To learn more, visit our Earning Credit Page
Not sure what college you want to attend yet? Study.com has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.
Back To Course
MCAT Prep: Help and Review90 chapters | 1011 lessons | 73 flashcard sets
{{courseNav.course.topics.length}} chapters | {{courseNav.course.mDynamicIntFields.lessonCount}} lessons | {{course.flashcardSetCount}} flashcard set{{course.flashcardSetCoun > 1 ? 's' : ''}}
Next Lesson
