Do you hate to get shots? Most of us do. It's hard to imagine anyone really enjoying getting poked with a sharp needle, right? But parents and doctors will tell you that shots are necessary.

Sometimes shots help you to feel better when you're sick. At other times, though, they help to immunize your body, so that you never get sick in the first place. Have you ever thought about what it means to be immune?

Your immune system works hard to defend your body against attacks all the time. Sometimes it needs a little help to fight certain types of illnesses. That's where immunization shots can come in handy.

Your body's immune system fights against germs and other tiny organisms that attack the body every second of every day. It's made up of a wide variety of special cells, proteins, and organs. It does an incredible job of protecting against infections and keeping you healthy most of the time.

Occasionally, foreign substances called antigens will invade the body. Their presence inside the body triggers the immune system to start a process — called the immune response — which will attack the antigens in order to prevent infection and disease and keep the body healthy.

The immune system's primary defense cells are white blood cells, which are also known as leukocytes. Leukocytes can be found throughout the body, including lymph nodes, the thymus, the spleen, and bone marrow.

When an antigen is detected in your body, the immune response starts. Leukocytes create specialized proteins called antibodies that attach themselves to the antigens. Leukocytes also memorize the antigens, so that they can immediately produce necessary antibodies the next time the same antigens are detected.

This memorization function is why, once you get a particular disease, such as chickenpox, you usually don't get it again. You become immune to it, because your immune system is already familiar with it and knows how to fight it as soon as it's detected.

Scientists figured out long ago that this memorization function could also be used to immunize people from diseases before ever getting them. Those immunization shots you get introduce antigens into your body in a variety of ways that won't make you sick.

Often, the antigens are weakened or dead germs that your body can fight off easily. In doing so, your body builds up antibodies that can protect you and prevent you from getting a particular disease in the future. This protection against harmful antigens is what it means to be immune.

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