1. The Immune System

2. What is a pathogen?
Disease-causing organisms that can be
present in air, water, food
Pathogens are viruses, bacteria, fungi, protists, and parasites
Microbe= microscopic organism or microorganism such as bacteria
What is a disease?
Any condition that prevents the body from working as it should/No Homeostasis!!
What causes a disease?
Pathogens, cancer, toxic substances, poor nutrition, organ malfunction, inherited disorders, or risky personal behavior

3. 4. What is an infection?
Person has symptoms and medical signs of being infected by pathogen
5. What is the Immune System?
The body’s primary defense against
disease-causing pathogens that enter body
Immune system makes WHITE BLOOD
CELLS and ANTIBODIES to destroy pathogens

4. Fighting Infectious Diseases:
Nonspecific defenses: First line of Defense-
Do not discriminate between one threat and another.
Examples
THE SKIN – the body’s most important line of defense
Mucus, saliva, tears- contain enzymes to break down the cell walls of many bacteria
Stomach acid – destroy pathogens that make it as far as your stomach

7. Specific Defenses: Second Line of Defense
Attack particular disease causing agents (pathogens)
Kill foreign substances that enter body (shape-specific antibody production response)
The reaction of the body to particular pathogens

8. 6. What is passive immunity?
Antibodies passed from mother to child through breast milk
7. What is active immunity?
Developed when exposed to antigen from fighting infection (example- chicken pox) or from antigen in vaccines (shots)
8. What is a Toxin?
Toxins are the poisonous wastes of
certain pathogens like bacteria
Toxins act as antigens

9. White Blood Cells (Leucocytes/Lymphocytes)
Cells made by immune system to destroy pathogens, toxins, cancer cells
What are phagocytes
or macrophages?
White blood cells that
engulf and digest
pathogens

11. Antigens
Protein molecule found on the cell membrane of a pathogen or cancer cell
Antigens cause immune system to react to presence of pathogens, toxins, cancer cells

12. Antibodies
Proteins made by WBCs that recognize and bind to antigens on pathogens.
Carried through the bloodstream to attack the pathogen causing the infection.
Antibodies attack invaders or mark them for destruction by other white blood cells- killer cells

13. Killer cells

14. Active immunity

15. What are vaccines?
Consists of a weakened or dead pathogen OR an antigen from pathogen
Injected into the body to stimulate immune system to produce antibodies that will kill pathogen that enter body in future

16. How do vaccines work?
After entering body, antibodies are produced for that specific pathogen.
After vaccination, immune system remembers pathogens by producing memory white blood cells that protect body for years.
Memory white blood cells react quickly when invasion of same pathogen occurs.

18. Allergies What causes an allergic reaction?
What is an ALLERGY?
A reaction to some substance (allergen) in environment that causes runny nose, sneezing, rash, or swelling
What causes an allergic reaction?
Caused by allergens that are normally harmless

20. Antibiotic Resistance= trait that pathogens inherit (DNA) that allows them to not be harmed by antibiotics
ANTIBIOTICS: drug that will kill
pathogens like bacteria (not viruses)
Trait: Antibiotic Resistance
Pathogens are able to survive when exposed to antibiotics

21. Immune system Video KidsHealth.org