1. Immune system
April 2016

2. Infectious Diseases
Diseases that are caused by agents that have invaded the body.
The immune system identifies these agents and defends itself.

3. First Line of Defense
Nonspecific defenses help protect the body against any pathogen* regardless of its identity.
Most pathogens must enter the body to cause disease.
The skin serves as a physical barrier.
Mucous membranes are epithelial tissues that protect the interior surfaces of the body.
Line the respiratory and digestive systems.
*any agent that causes disease- bacteria, viruses, protists, fungi

4. Second Line of Defense
If a pathogen gets past the skin and mucous membranes, the second line of defense is nonspecific immunity.
Includes inflammatory response and temperature response.
Like the first line of defense, these second line defenses are nonspecific: they work the same way against any pathogen.

5. Inflammatory Response
The inflammatory response is a series of events that suppresses infections and speeds recovery.
Histamine increases blood flow to the injured area and increases permeability of the capillaries causing redness, swelling, warmth, and pain.
Fluids and white blood cells called phagocytes pass through the capillary walls to the injured area ingesting and destroying foreign matter.

6. Temperature Response A rise in body temperature above normal
(98.6˚F) is called a fever.
Fever is a symptom of illness that shows the body is responding to an infection.
Some pathogens trigger fever, as do chemicals released by some phagocytes.
A moderate fever may slow bacterial and viral activity and promote white blood cell activity.
However, a very high fever is dangerous because extreme heat can destroy important cellular proteins.
Temperatures greater than 103˚F can be dangerous and greater than 105˚F can lead to death.

7. Third Line of Defense: Specific Defenses
Although the nonspecific defenses usually keep pathogens from harming the body, a pathogen sometimes breaks through.
In response, the body begins its third line of defense, a response aimed specifically at the pathogen.
The immune system provides the body’s specific defenses by recognizing and attacking foreign substances in the body.

8. Immune System
Components of the immune system include bone marrow, thymus gland, lymph nodes, spleen, tonsils, and adenoids.
The white blood cells of the immune system are called lymphocytes.

9. Bone Marrow & Spleen
Bone marrow found inside long bones, makes billions of new lymphocytes needed by the body every day.
The spleen, the largest lymphatic organ in the body, stores healthy blood cells, breaks down aging red blood cells, and helps develop lymphocytes.

10. Recognizing Pathogens
Lymphocytes can provide specific defenses because they recognize foreign invaders.
An antigen is any substance that the immune system can recognize and react with.
When lymphocytes recognize an antigen, they bind to the antigen and start a specific attack.
The reaction of the body against an antigen is known as an immune response.