Antibacterial Mechanisms

Question 1

What is an example of a biochemical mechanism used as defence against pathogens?

Answer 1

Sebaceous gland secretions - fatty acids, enzymes, antibacterial defences

Question 2

What is the difference between commensal and pathogenic microbes?

Answer 2

Commensal: good bacteria

Pathogenic: bad bacteria

Question 3

What is the purpose of the lymphatic drainage?

Answer 3

It drains white blood cells & carries them around the body.

Question 4

What is the purpose of post-capillary venules?

Answer 4

They can open to allow plasma proteins/leukocytes to escape from the blood.

Question 5

What 4 things are associated with acute inflammation?

Answer 5

1. Tumor: swelling
2. Calor: heat
   3: Rubor: redness
   4: Dalor: pain

Question 6

What is the complement system?

Answer 6

Complement is a protein made in the liver, which can be activated by pathogens/antibodies.
It enhances the ability of phagocytes/microbes to clear pathogens.

Question 7

What on the microbes cell surface activates the complement system, and what process occurs after?

Answer 7

PAMPS (pathogen associated molecular patterns) activate the system, and phagocytosis takes place.

Question 8

What do component parts of the complement system break down into?

Answer 8

They break down into bits of complement.

E.G. complement 1 can be broken down into 2, 3, 4, 5, etc

Question 9

Which 2 complement proteins are involved in inflammation?

Answer 9

C3a & C5a.

Question 10

What is C3b responsible for?

Answer 10

Opsonisation of phagocytosis, which sticks to the pathogen & engulfs it.

Question 11

What are the 3 possible effects of complement activation?

Answer 11

1. Opsonisation & phagocytosis
   - C3b or C4b bind to microbe
   - Phagocyte with a C3b receptor recognises this
   - Phagocytosis of microbe occurs
2. Stimulation of inflammatory reactions
   - C3b binds to microbe, C3a & C5a is released
   - These recruit & activate leukocytes
   - Destruction of microbe via leukocytes occurs
3. Complement-mediated cytolysis
   - C3b binds to microbe & activates late components of complement
   - Formation of MAC (attack complex) occurs
   - Osmotic lysis of bacteria occurs

Question 12

What are C3a, C4a & C5a collectively known as?

Answer 12

Anaphylatoxins.

Question 13

Which 2 complement fragments act on mast cells to release histamines?

Answer 13

C3a and C5a.

Question 14

What causes the redness and heat during inflammation?

Answer 14

Vasodilation, which also increases the vol. of WBCs to the area.

Question 15

What causes swelling in inflammation?

Answer 15

Blood vessels become leaky with water, which causes the swelling.

Question 16

What 2 things does C3a, C4a and C5a induce?

Answer 16

1. Acute inflammation

2. Chemotaxis (movement of cells in response to a stimuli)

Question 17

Which pro-inflammatory cytokines can induce the production of complement, and which type of cell releases them?

Answer 17

Macrophages can release TNF-alpha and IL-1 to send to the brain & cause a fever.

Question 18

Which pro-inflammatory cytokine can be activated/released by NK cells?

Answer 18

IFN-gamma

Question 19

When are lymphocytes activated?

Answer 19

When the innate response is not enough to fight the pathogen.

Question 20

What is the process in which the adaptive immune response is activated?

Answer 20

1. Dendritic cells mature & increase their antigen presenting capability
2. Dendritic cells & immature T helper cells meet in the lymph nodes
3. Toll-like receptors binding to phagocytes activate more cytokines
4. Macrophages can also act like APC’s localised at the site of the infection
5. Adaptive immune response is then activated

Question 21

What do MHC molecules do?

Answer 21

They display antigens, which are required for a full T cell response.

Question 22

Where are naive T cells generated?

Answer 22

In the thymus, where they have not interacted with an APC yet.

Question 23

Where do naive T cells reside?

Answer 23

In the lymph nodes.

Question 24

What can activation of T cells stimulate?

Answer 24

1. Stimulation of B cells (producing antibodies)
2. Cytotoxic T cells
3. Cytokines
4. Effector T cells

Question 25

What do B cells turn into?

Answer 25

They turn into plasma cells which are bigger & produce antibodies.