Q2P: 1-5
Distinguish between the two main types of host defense mechanisms and give specific examples.
I. Nonspecific: attacks any foreign substance or invader. Example: Fever, Phagocytosis, Inflammation
II. Specific: attacks a specific foreign substance or invader. Example: T and B Lymphocytes, Antibodies
Describe how the respiratory tract defends against pathogens.
The respiratory tract contains nasal hairs, mucous membranes, and irregular chambers of the nose that trap inhaled debris.
- Lysozyme and other enzymes that lyse or destroy bacteria are present in nasal secretions, saliva, and tears.
- Swallowing of saliva removes microbes from the oral cavity.
What is microbial antagonism? Describe three ways it fights against pathogens. What medical treatment decreases microbial antagonism and how?
Microbial antagonism occurs when resident microbes of the indigenous microbiota prevent colonization by new arrivals to a particular anatomical site. Microbial antagonisms fight against pathogens by competing for colonization sites, nutrients, and producing substances that kill other bacteria. Long-term use of broad-spectrum antibiotics can decrease microbial antagonism and lead to superinfections.
Describe three ways in which the body raises its temperature.
1. Increased thermostat causes vasoconstriction (decreased diameter of blood vessels)
2. Shivering (involuntary skeletal muscle contraction)
3. Increased metabolism
True or False. Rabbit interferon will work just as well as human interferon in the human body.
False. Interferons are host- or species-specific.
Distinguish between the first, second, and third lines of host defenses and give specific examples.
The first and second lines of defense are the non-specific host defenses. (They are innate or inborn and are unique to the species.)
The third line of defense (the immune system) is the specific host defenses that are acquired.
Where is the mucociliary escalator found and how doe sit work against pathogens?
The mucociliary escalator is located in the respiratory system. The cilia present on epithelial cells lining the respiratory tract sweep trapped dust and microbes upward toward the throat, where they are expelled by sneezing, spitting, and coughing.
What is transferrin and where do you find it in the body? How does it specifically fight against pathogens?
Transferrin is a protein found in the blood that has a high affinity for iron. Its normal function is to store and deliver iron to host cells. It is a nonspecific host defense mechanism because it sequesters iron and deprives pathogens of this essential nutrient.
List at least 5 benefits of a fever.
1. Raises body temperature above the optimal growth rate for some pathogens (slows growth or may kill some pathogens).
2. Chemicals released during fever cause a decrease in plasma iron concentration (required by most microbes to grow).
3. Enhances phagocytosis (spring cleaning).
4. At higher temperatures, microbial enzymes or toxins may be inactivated.
5. Patient feels ill thereby he/she lowers activity and energy is directed to fight infection.
True or False. Rabbit interferons will work just as well as human interferon in the human body.
What is the major physical or mechanical barrier to pathogens?
Intact, unbroken skin and mucous membranes are a major physical or mechanical barrier to pathogens.
Describe at least 7 factors in the digestive tract that defends against pathogens.
1. Digestive Enzymes
2. Stomach Acidity (pH ~ 1.5)
3. Alkalinity of the intestines
4. Mucus
5. Phagocytes
6-7. Peristalsis and expulsion of feces also remove bacteria from the intestines.
What is a fever? How could a fever above 109F cause death?
A fever is considered a body temperature above 37.8C (100F). A fever above 109F could cause death because that temperature denatures proteins of its nutrients. It can also cause seizures.
Should a normal healthy adult take medication to reduce fever of 101F? Explain why or why not.
It is not necessary for a normal healthy adult to take medication to reduce a fever of 101F. Medicating a fever can delay recovery. Fever is beneficial and should run its full course. Antipyretics should only be considered if the temperature goes above 103F (40C).
What are cytokines? Give three specific examples.
Cytokines are a broad term for small proteins that act as chemical mediators in the body. They act as chemical messengers within the immune system and between the immune system and other systems of the body. (Examples: Interferons, interleukins, and chemokines.)
Describe at least 5 factors in the skin that defend against the pathogens.
1. Dryness
2. Acidity (pH ~ 5.0)
3. Temperature (<37C degrees)
4. Sebum (secreted by sebaceous glands and contains fatty acids toxic to some pathogens.
5. Perspiration flushes microbes from the skin and contains lysozyme.
Describe how the urinary tract defends against pathogens.
The Urinary tract is usually sterile except for the distal part of the urethra (farthest part from the bladder). Microbes are continually flushed from the urethra by frequent urination. (Urinary infections result from infrequent urination, dehydration, not urinating after sexual intercourse, enlarged prostate gland [decreases the flow of urine].)
What is pyrogen? Distinguish between an exogenous vs. endogenous pyrogen and give a specific example of each.
Pyrogens are substances that stimulate the production of a fever.
Exogenous pyrogen: Comes outside the body. (Example: pathogens and substances they produce/release; endotoxin, bacterial toxins)
Endogenous pyrogen: Originates from inside the body. (Example: interleukin-1 (IL-1), a cytokine that is produced by certain white blood cells.)
What are interferons and when are they normally produced?
Interferons (alpha, beta, and gamma) are proteins that are produced by different stimuli and different cell types in the body.
What is the complement system and how does it play a role in host defense?
The complement system is a set of 30 proteins (including nine proteins designated C1-C9) found in the blood plasma that plays a key role in host defense. It is "complementary" to the action of the immune system.
Describe at least four factors in mucous membranes that defend against pathogens.
1. Sticky and traps invaders
2. Contains Lysozyme
3. Contains Lactoferrin
4. Contains lactoperoxidase, an enzyme that generates superoxide radicals, highly reactive forms of oxygen, which are toxic to bacteria.
What is lysozyme and what does it specifically target? What type of microbe would be most susceptible to lysozyme? Where in the body would you find lysozyme?
Lysozyme is an enzyme that breaks down peptidoglycan in bacterial cell walls, specifically in gram-positive bacteria. It is found in the skin during perspiration and mucous membranes, specifically mucus.
Where is the body's "thermostat"? What specific molecule induces the "thermostat" to raise the body's temperature?
IL-1 stimulates the hypothalamus of the brain to raise the body’s thermostat.
Describe how interferons decrease the spread of viral infection.
The interferons produced by a virus-infected cell bind to adjacent uninfected cells, causing them to produce antiviral proteins (AVPs). The antiviral proteins do NOT inhibit infection with the virus but do "interfere" with the viral replication thus limiting the spread of the virus.
True or False. Complement is a slow defense mechanism that specifically works against parasitic worm infections.
False. The action of the complement system is rapid and non-specific - it exerts the same defensive effects on any microbe that has invaded the body.