Lecture 1 part 4

Question 1

What do bacteria need to survive/replicate?

Answer 1

Suitable environment

Source of nutrients

Protection from harmful elements (virulence mechanisms)

Note: Virulence mechanisms allow a pathogen to outcompete host cells and resist their defense

Question 2

What are the factors affecting infection?

Answer 2

Type of agent

Virulence of agent

Means of exposure

Dose of the agent

Susceptibility of host to agent

Question 3

List some of the innate defense mechanisms.

Answer 3

Barriers to infection

Phagocytic cells

Complement

Native defense cytokines

Natural killer (NK) cells

Question 4

List some of the adaptive defense mechanisms.

Answer 4

Humoral=antibodies

Cell-mediated immunity: T-helper cells (cytokines), Cytotoxic T-cells, Gamma-Delta T-cells

Question 5

Describe the process of acute inflammation.

Answer 5

1. ) Tissue damage causes release of vasoactive and chemotactic factors that trigger a local increase in blood flow and capillary permeability.
2. ) Permeable capillaries allow an influx of fluid (exudate) and cells.
3. ) Phagocytes migrate to site of inflammation via chemotaxis.
4. ) Phagocytes and antibacterial exudate destroy bacteria.

Question 6

What are the major innate and adaptive defense mechanisms against extracellular pathogens?

Answer 6

Innate: Complement activation, Phagocytosis by phagocytes, Extracellular killing

Adaptive: B-cells and Helper T-cells, Antibodies (humoral)

Question 7

What are the major innate and adaptive defense mechanisms against intracellular pathogens?

Answer 7

Innate: NK cytotoxicity

Adaptive: Cytotoxic T-cells (cell mediated), Macrophage and Helper T-cell (cell mediated)

Question 8

List the anatomical and physiological barriers of the innate immune system.

Answer 8

skin

mucus

normal gut flora

stomach acid

antimicrobial peptides (defensins)

Question 9

List some of the benefits of having microflora in the gut.

Answer 9

Excludes harmful pathogens

Important in the proper development of lympoid organs

Regulate B and T cell function

Note: if you lose normal gut flora you increase the likelihood of infection.

Question 10

What immunoglobulin is found in mucus?

Answer 10

IgA

Question 11

Name the two examples given in class of when barriers are disrupted.

Answer 11

Keratoconjunctivitis sicca (dry eye)

Foot rot

Question 12

Give a list of the cells that participate in innate immune defense.

What are sentinal cells able to detect?

Answer 12

Phagocytic cells: Neutrophiles and Macrophages

Sentinal cells: Dendritic cells, Macrophages and Mast cells

Sentinal cells are able to detect PAMPs.

Question 13

List some of the antibacterial actions of neutrophils.

Answer 13

1. ) Lysozyme (bactericidal)
2. ) Defensins (bactericidal)
3. ) Lactoferrin (binds iron)
4. ) Collagenase (degrades bacteria and tissue)
5. ) Gelatinase (degrades bacteria and tissue)
6. ) Myeloperoxidase (Respiratory burst)

Question 14

Name the 3 pathways of complement activation

Answer 14

Classical pathway

Lectin pathway

Alternative pathway

Question 15

What is the end product common to all 3 complement pathways?

Answer 15

Membrane attack complex (MAC).

Question 16

True or False: IgM is more efficient at initiating the classical pathway than IgG.

Answer 16

TRUE.

Because IgM is a pentamer, it does not require multiple antibodies to activate C1.

Question 17

Which complement protein is highest in concentration in the blood?

Answer 17

C3.

Question 18

What is the function of the membrane attack complex (MAC)?

Answer 18

Creates a pore in a cellular membrane, leading to cellular lysis.

Question 19

Which complement activation pathway is reliant on the adaptive immune system?

Answer 19

Classical pathway

Requires antibodies for C1 binding.

Question 20

True or False: The lectin and alternative pathways can be activated without the presence of antibodies.

Answer 20

TRUE

These pathways are considered as part of innate immunity.

Question 21

Which complement molecule is responsible for opsonization of pathogens for later recognition by phagocytic cells?

Answer 21

C3b

Question 22

Describe the process occuring here.

Answer 22

Two IgG molecules are bound to a membrane. C1 has cross-linked the two IgGs, causing a conformational change in C1 to expose its active site.

Question 23

C5 convertase cleaves C5 into C5a and C5b. What are the major functions of C5a?

Answer 23

Phagocyte chemotaxis

Mast cell degranulation

Neutrophil activation

Question 24

What is the function of mannose-binding lectin (MBL)?

Answer 24

Binds to mannose molecules present on pathogen surfaces.

Functionally similary to C1. Initiates the lectin pathway of complement activation.

Question 25

How is the alternative pathway activated?

Answer 25

C3 in the plasma slowly degrades into C3a and C3b on a regular basis. If C3b binds to a microbial surface, Factor B will bind, creating a C3 convertase (different molecule, but same action as in the other 2 pathways).

This results in more C3 cleavage and activation of the complement system.

Question 26

In general, what are the four biological consequences of complement activation?

Answer 26

Cell lysis

Vasodilation / Increased vascular permeability

Chemotaxis

Opsonization