Immune system protection inside the body

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

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

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

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

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

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