1. Immune system protection inside the body

2. Lymphocytes: white blood cells that help the body fight pathogens
B cell: white blood cell that produces antibodies
Helper T cell: WBC that signals B cells to produce antibodies
Antibody: special protein that helps fight infection
Macrophage: WBC that surrounds and destroys pathogens

3. Cycle of fighting a pathogen
Pathogen invades body  helper T cells send signals to B cells  produces antibodies 
B cells enter the lymph nodes and lymph tissues antibodies travel through the blood to destroy pathogen destroyed pathogens enter lymph, filtered in lymph nodes, and removed by spleen

4. IMMUNITY The body’s resistance to disease-causing agents
Active immunity: resistance to disease due to the presence of antibodies
Vaccine: substance containing dead or weakened pathogens
Passive immunity: results from introducing antibodies into a person’s bloodstream; short-term and used when risk of developing disease in immediate

5. PATHOGENS A germ that causes disease
Communicable disease or infectious disease: illness caused by pathogens that can be spread from one living thing to another
Bacteria: single celled microorganism; can be beneficial; those that are harmful cause disease by releasing toxins into the body
Fungi: single and multi celled parasitic organisms; obtain their food from organic materials

6. Viruses: one of smallest known pathogens; takes over the cell and causes it to make more viruses; newly produced viruses are released and take over other cells
Protozoa: tiny, single-celled organisms that produce toxins that cause disease

7. HOW PATHOGENS ARE SPREAD
Direct contact
Through the air
Contact with contaminated objects
Handling or being bitten by an insect or animal carrying the pathogen
Contact with contaminated food and water