1. NOTES: The Immune System (UNIT 10 part 2)

2. • PATHOGEN: a disease-causing agent; causes infection
-pathogens include:
viruses fungi
bacteria protozoans

3. Background Pathogen Info: Bacteria vs.Virus
*Alive (1 celled organism)  take ANTIBIOTICS to slow their growth
*Not alive, therefore no antibiotics
*Viruses “hijack” cells & use the cells’ machinery in order to reproduce (use cells’ ribosomes. ATP, amino acids, etc.)
* 2 types: 1. hijacker (cold)
2. hijacker & infiltrator (HIV)
*VACCINES prepare your immune system in case you are exposed to that virus later (can be difficult to develop due to high # of virus mutations)

4. Examples of bacteria that cause infection:
E. coli
Salmonella
Staphylococcus
Examples of viruses that cause infection :
Papovavirus – papilloma (warts)
Adenovirus – respiratory diseases
Herpes virus – herpes
Poxvirus – smallpox
Parvovirus – roseola
Picornavirus – polio
Rhinovirus – common cold

5. The body has nonspecific and specific defenses against infection.
Why don’t YOU have mold on your skin???

6. Nonspecific Defenses:
• general defense
• provide protection against many different pathogens
• involve physical and chemical barriers, fever, inflammation, phagocytosis

7. Specific Defenses: • very precise • target certain pathogens
• also known as ACQUIRED IMMUNITY
• involve specialized lymphocytes (T cells and B cells) that recognize and respond to specific pathogens
**nonspecific defenses are quick to respond; specific defenses are slower to respond

8. NONSPECIFIC DEFENSES 1) Species Resistance
• each species is resistant to certain
diseases that may affect other species
• examples: measles, mumps,
gonorrhea, and syphilis infect
humans but not other animal species
• one species may be resistant to a disease that affects another species because its tissues somehow fail to provide a suitable environment for the pathogen (temperature, chemical environment, etc.)

9. 2) Mechanical Barriers = FIRST LINE OF DEFENSE (keep out!)
● mechanical barriers / physical barriers include:
-skin (and associated hairs)
-mucous membranes
-fluid (sweat and mucus)
● as long as they remain intact, they can keep out many pathogens

11. **all other “nonspecific defenses” are considered the SECOND LINE OF DEFENSE (pathogen inside…. destroy!)

12. 3) Phagocytosis –removes foreign particles from the lymph and blood
• the most active phagocytes in blood are NEUTROPHILS and MONOCYTES
• Monocytes give rise to MACROPHAGES

14. • MACROPHAGES are found in the linings of blood vessels in the:
-bone marrow
-liver
-spleen
-lungs
-lymph nodes

15. 4) Chemical Barriers
• gastric juice: contains hydrochloric acid (HCl) and enzymes (e.g. pepsin) that are lethal to pathogens
• tears: contain the enzyme LYSOZYME
(which has antibacterial action)
• the salt in perspiration accumulates on the skin and kills bacteria on the skin

16. 4) Chemical Barriers (cont.)
• INTERFERONS: chemicals released by virus-infected cells; they bind to receptors on uninfected cells; block virus replication

17. 5) Fever
• higher body temperature increases the rate of phagocytic cells
• also lowers iron levels in the blood (bacteria and fungi require iron, so this slows their growth)
*adults: go to doctor if over 103°F or is high and lasts more than 3 days
*children older than 4months: go to doctor if over 104°F

18. 6) Inflammation • a tissue response to injury or infection
• chemicals released by damaged tissues attract WBCs to the site & make capillaries more permeable
• produces: localized redness, swelling, heat and pain
 the mass of WBCs, bacterial cells, and damaged tissue forms a thick fluid called PUS

21. REVIEW QUESTION:
Which of the following is NOT a nonspecific defense? A) Gastric juice B) Lysozyme found in tears C) fever D) Macrophages (phagocytic cell) E) Skin F) All of nonspecific defenses

22. REVIEW QUESTION:
Which of the following is NOT part of the 1st line of nonspecific defense?
Gastric juice
Skin
Sweat
Mucus membranes

23. REVIEW QUESTION:
TRUE or FALSE: Interferons are a chemical defense (part of 2nd line of defense) and they are released by virus- infected cells.

24. REVIEW QUESTION: How do antibiotics work?
By interfering with a bacteria’s ability to divide or survive.
By interfering with a virus’ ability to divide or survive.
By increasing the number of “good cells” in your body.
A and B
All of the above

25. REVIEW QUESTION: What causes inflammation? A tissue injury
Broken/damaged lymph capillaries
Infection
A and C
All of the above