1. Immune System
Is a network of cells, tissues, organs and chemicals that fights off pathogens.

2. Physical and Chemical Barriers
These two elements are the body’s first line of defense to
prevent pathogens from entering and causing disease.
Skin- Few pathogens can pass through the tough layer of dead skin cells that surrounds the body.
Tears and saliva-contain enzymes that destroy or disable many pathogens.
Mucous membranes-Is a sticky substance that traps pathogens. It carries the trapped pathogens to other areas of the body for disposal. (mouth, nose, bronchial tubes)
Cilia-hair-like projections that sweep mucus and pathogens to the throat to be swallowed or coughed out.
Gastric juice-in the stomach destroys pathogens that enter the body through the nose and mouth.

3. Inflammatory Response
Is a reaction to tissue damage caused by injury or infection. Its purpose is to prevent further tissue injury and to halt invading pathogens.
Example: when a splinter enters your body, your body immediately reacts to the damage caused by the splinter.

4. Phagocyte (FA-guh-site)
A white blood cell that attacks invading pathogens.
(Pus, a collection of dead white blood cells and damaged tissue is at the site of inflammation as a response to bacteria).

5. Specific Defenses Specific defenses react to invasion as a
result of the body’s ability to recognize
certain pathogens and destroy them.
The Immune Response is an interaction
between your body and an invading
pathogen.

6. Stages of Immune Response
Pathogen invades the body
Macrophages engulf the pathogen
Macrophages digest the pathogen and T cell recognize antigens of the pathogen as an invader
T cells bind to the antigens.
B cells bind to antigens and helper T cells.
B cells divide to produce plasma cells
Plasma cells release antibodies into the bloodstream.
Antibodies bind to antigens to help other cells identify and destroy the pathogens.

7. Antigen
During the immune response, certain types of white blood cells react to antigens (type of protein), which is a substance that triggers an immune response.
Immunity is the state of being protected against a particular disease.

8. Lymphocytes
Is a specialized white blood cell that coordinates and performs many of the functions of specific immunity.
Two types of Lymphocytes.
Helper T Cells-trigger the production of B cells/Killer T cells.
Killer T Cells-attack and destroy infected body cells. They attack only the infected cells.

9. Antibody Is a protein that acts against a specific antigen.
Active Immunity-is the immunity your body develops to protect you from measles or from other diseases. Active immunity develops when the body is exposed to antigens from invading pathogens.
Vaccine-a preparation of dead or weakened pathogens that are introduced into the body to stimulate an immune response.
Inactive immunity-the body receives antibodies.

10. Review
1. List three physical and chemical barriers that pathogens encounter when they try to enter the human body.
2. What is the difference between active immunity and passive immunity.
3. Where can you go to find out which immunizations you need?