1. The Immune System

2. The Body’s Defense Pathogens are everywhere.
We stay healthy because our body has defenses to keep pathogens out.
The immune system fights infection through the production of cells that inactivate unwanted cells
A lymphocyte engulfing an invader

3. Nonspecific Defenses fight or defend against any pathogen
First line of defense:
Skin
Mucus
Sweat
Tears
Second line of defense:
inflammatory response
fever
interferons (fight viruses)

4. Specific Defenses guard against certain invaders
When a pathogen gets past the body’s nonspecific defenses, the immune system attacks.
The antigen (invader) triggers the immune response.
Future attacks will be met by memory cells

5. Organs of the Immune System

6. Humoral Immunity-B cells
B lymphocytes (B cells) provide immunity against antigens and pathogens in body fluids
B cells recognize invader and produce large numbers of plasma cells and memory B cells
Plasma cells release antibodies
Antibodies are proteins that recognize & bind to antigens
As antibodies overcome infection, plasma cells die off and stop producing antibodies
Memory B cells remain in blood stream so they can make plasma cells immediately if ever exposed to the same pathogen again

7. Cell Mediated Immunity-T Cells
Killer T cells track down and destroy bacteria, fungi, protists, or other foreign tissue.
Primary defense against the body’s own cells when they have become cancerous or infected by pathogens
Helper T cells produce memory T cells.
Memory T cells will attack if the same pathogen ever returns.
Suppressor T cells shut down the killer T cells when the infection is under control.

8. HIV attacks T cells
HIV (Human Immunodeficiency Virus) attacks the body’s T cells.
The immune system is disabled.
Victim is not able to fight infection
HIV eventually causes AIDS

9. Vaccines Edward Jenner invented first vaccine in 1769
Injected boy with cowpox virus (weak similar virus to smallpox)
Later injected with deadly smallpox virus.
Boy had immunity to the virus
Vaccines are weakened or “killed” virus or bacteria pathogen.
The body responds by creating an immunity to the pathogen (antibodies)