Lecture 8

Question 1

How does mucus membrane resist pathogens?

Answer 1

• mucous washes away microorganisms

- constant shedding of cells

Question 2

How do interferons help detect/prevent infection?

Answer 2

• infected cell releases interferons (signal)
• this signal triggers:
• • reduced protein synthesis (via destruction of RNA)
• • apoptosis
• • activates immune cells

Question 3

Which PAMP does TLR-3 respond too?

Answer 3

• responds to double stranded RNA found in viruses

Question 4

Alternative Pathway

Answer 4

Small amount of C3 spontaneously breaks into C3a and C3b. C3b binds to endotoxin and glycoproteins on bacterial surface where it is stabilized and stimulates conversion of more C3 to C3a and C3b

Question 5

________ and ________ prevent infection of of the genitourinary tract

Answer 5

• flow of urine

- lactobacillus

Question 6

Antimicrobial Proteins/Peptides

chemical defense

Answer 6

• Lysozyme
• Lactoferrin
• Defensin

Question 7

3 antimicrobial proteins/peptides

Answer 7

• Lysozyme
• Lactoferrin
• Defensins

Question 8

How does the gastrointestinal prevent infection from pathogens?

Answer 8

• Stomach has very low pH (pH of stomach = 2)
• bile from liver
• digestive enzymes (catabolism of protein, carbohydrates, fats)

Question 9

Interferons

Answer 9

• signaling protein (early warning system)
• are produced in response to an infection
• class cytokines which are soluble proteins that signal between cells

Question 10

Classical Pathway

Answer 10

Antibody binding to antigen triggering conversion of C3 to C3a and C3b

Question 11

Out of the two physical barriers, which one is more susceptible for infection?

Answer 11

mucous membrane

Question 12

How does indigenous microbiota prevent colonization of parasitic microorganisms?

Answer 12

• Provide competition for nutrients
• Provide competition for attachment sites
• Secrete acid and bacteriotoxin

Question 13

Function of C5a

Answer 13

• acts as chemoattraction for phagocytes

Question 14

How do defensins prevent infection?

Answer 14

• small peptide that form pores in bacterial membrane g(+, and -)

Question 15

How can antibiotic induced colitis occur?

Answer 15

• antibiotic kill normal flora

Question 16

Activation of classical pathway

Answer 16

Antibody binds to antigen and triggers conversion of C3 to C3a and C3b

Question 17

Immune system (2 types)

Answer 17

Innate –nonspecific and rapid

• Indigenous microbiota
• Physical barriers
• Chemicals
• Cellular

Adaptive – specific for certain organisms, (not born with it) takes time to develop

Question 18

Clostririum Difficile

Answer 18

• opportunistic parasite
• will outcompete attachment sites and nutrients when body is weakened by antibiotics
• cure: fecal transplant

Question 19

Toll-like Receptors

Answer 19

• bind with PAMP and trigger immune response

Question 20

Which PAMP does TLR-4 respond too?

Answer 20

• Lipid A (found in gram (-) bacteria)

Question 21

Function of C3b, and C4b

Answer 21

• opsonization

- flag pathogen for phagocytosis

Question 22

Function of C3a and C5a

Answer 22

pro inflammatory

- binds to mast cell and causes release of histamine

Question 23

What makes skin resist pathogens?

Answer 23

• low in pH/nutrients (poor source of carbon), dry, salty/oily
• covered in normal flora (competition)
• shedding of dead skin
• production of antimicrobials (fatty acids, acids, sweat)

Question 24

Staphylococcus epidermis

Answer 24

• part of skin barrier

- produces acidic by-proucts (making skin more acidic)

Question 25

How does respiratory prevent infection from pathogens?

Answer 25

- Turbulent air (in nose) causes microorganism to get stuck in nasal hair and mucous membrane - Mucous ladder in respiratory tract

Question 26

Activation of alternative pathway

Answer 26

- spontaneous degradation of C3 to C3a and C3b | - C3b recruits more C3 for degradation

Question 27

Lectin

Answer 27

Lectins (polysaccharide binding proteins) bind to mannose (type of sugar not found on human cells) on invading cells surface triggering conversion of C3 to C3a and C3b

Question 28

How do indigenous microbiota act as a defense in the innate immune system?

Answer 28

- They prevent pathogens from colonizing

Question 29

Physical barriers of immune system

Answer 29

- Skin | - Mucus membrane (lines tubes)

Question 30

How does lactobacillus prevent infection from pathogens?

Answer 30

- lowering pH | - lactobacillus ferments glycogen and produces acetic acid and lactic acid

Question 31

How do lactoferrin prevent infection?

Answer 31

- outcompete bacteria for iron | - iron is a cofactor for proteins (hemoglobin uses iron)

Question 32

Microorganisms that can resist stomach's acidity:

Answer 32

- geardia (Protozoal cyst) - Hepatitas A (virus) - Helicobacter pylori - Mycobacterium tuberculosis

Question 33

Function of C5b

Answer 33

- initiates MAC (membrane attack complex) | - MAC pokes holes in bacterial membrane

Question 34

PAMPs

Answer 34

Patogen associated molecular patterns | - ex: LPS, peptidoglycan, certain nucleotides

Question 35

Activation of Lectin pathway

Answer 35

- Lectin binds to mannose (sugar found on pathogen) | - which triggers degradation of C3 to C3a and C3b

Question 36

How do lysozyme prevent infection? | Where is lysozyme found

Answer 36

- breaks down peptidoglycan g(+) | - mucus, saliva, lacrimal fluid (tears)

Question 37

First defense line in innate immune system

Answer 37

Normal flora (Indigenous microbiota)