Immune System Study Guide

I. What is the Immune System?
A. Cells, tissues and organs work together to protect the body.
1. Antigen: A foreign substance that invades the body.
B. Leukocytes (loo-kuh-sytes) or white blood cells.
1. Leukocytes seek out and destroy organisms and substances that cause diseases.
2. Leukocytes are created and stored in many locations (called lymphoid organs):
3. Leukocytes travel throughout the body through lymphatic (lim-fah-tik) vessels.
a. Lymphatic vessels are like a highway connecting lymphoid organs and the lymph nodes.
4. Leukocytes also circulate through blood vessels.
5. There are two types of leukocytes:
a. Phagocytes (fah-guh-sytes): Chew up invading organisms.
b. Lymphocytes (lim-fuh-sytes): Allow the body to remember previous invaders.
1) There are two kinds of lymphocytes:
a) B lymphocytes: B cells seek out invaders, and create antibodies to lock unto invaders.
b) T lymphocytes: Are like soldiers, destroying invaders that the B lymphocytes identified. T cells are nicknamed killer cells. T cells mature in the thymus gland, near a person’s heart.

Be able to draw a picture of a B cell and a T cell working together to destroy an antigen.

II. Types of Immunity
A. Innate Immunity
1. Humans do not have to worry about many diseases that animals have.

B. Adaptive Immunity
1. Develops as generations are exposed to diseases or receives immunizations.

Question to consider: Why do you think many Native Americans became extremely ill when Europeans came to America?

C. Passive Immunity
1. As someone gets older, they become immune to germs they have come into contact with.

Question to consider: Do you think you will have more or less colds as you become older?

III. Immune System Difficulties
A. Allergies
1. Occurs when the immune system overreacts when being exposed to antigens.

Pay special attention to bold items.