1. Viruses and The Immune System

2. Human Immune System There are three levels of immune defense
Primary Line of Defense: Skin and mucous barriers that prevent pathogens from entering the body
Secondary Line of Defense: inflammatory response caused by an increase in WBC and fluids in a tissue
Tertiary Line of Defense: Defense mechanisms that specifically target each pathogen

3. Primary Line of Defense
The skin prevents pathogens from entering the body
Sweat and oils on the skin create an acidic environment that can destroy harmful pathogens
Mucous and cilia keep pathogens from entering through the mouth and nose

4. Secondary Line of Defense
If a pathogen is able to get past the primary line of defense a non-specific response is initiated
WBC and fluid leaks from the blood vessels in to surrounding tissues
WBC engulf and destroy pathogens
Cells produce interferon, this blocks the replication of viruses

5. Tertiary Line of Defense
Antigens are substances that trigger a specific immune response
Antibodies are produced to attach to a specific antigen
When antibodies have attached themselves to viruses the virus is unable to enter a cell
The virus/antibody structure is then engulfed and destroyed

6. Tertiary Line of Defense
B-cells produce the different antibodies that we have
Each B-cell only produces 1 type of antibody
Once an antigen is present the specific b-cell replicates rapidly and starts producing antibodies

7. Immunity
Once an antibody has been created we will always have a copy of it  we have immunity to that antigen
The initial response to a antigen is called the primary immune response
Subsequent exposures to an antigen trigger secondary responses

8. Vaccines
Vaccines introduce an antigen to the body to allow for antibodies to be produced and ready for infections
The first vaccine was created by Edward Jenner for small pox by injecting people with cowpox, a similar virus
Louis Pasteur developed vaccines that were weakened or destroyed versions of the antigen