Unit 2: Week 2

Question 1

Approximately how long after the innate immune response does the adaptive immune response begin?

Answer 1

3-4 days

Question 2

Name 3 cells that present MHC II.

Answer 2

Macrophages
Dendritic cells
B-cells

Question 3

When a dendritic cell has TLR recognition of a pathogen, what molecule is upregulated on its surface?

Answer 3

B7.1/B7.2

Question 4

Identify the co-stimulatory molecules on the surface of a naive CD4+ T-helper cell.

Answer 4

T-cell receptor
CD4
CD28
CD40Ligand

Question 5

How do most T-cells enter the lymph node?

Answer 5

Via high endothelial venules

Question 6

Describe the step by step process of T-helper cell activation by a dendritic cell presenting antigen.

Answer 6

1. T-cell receptor recognises the antigen
2. CD4 binds to MHCII
3. B7.1/B7.2 bind to CD28
4. This unregulates CD40L on the T-cell surface
5. CD40L binds to CD40
6. Dendrite secretes a polarising cytokine
7. T-cell secretes IL-2 as an autocrine to induce proliferation

Question 7

What is T-cell anergy and why does it occur?

Answer 7

Inactivation of T-cell when a dendritic cell presents without B7.1/B7.2 (because there was no TLR recognition of pathogen).

Prevents an immune response to phagocytic cells that present self molecules that are not pathogen.

Question 8

What polarising cytokine and transcription factor are responsible for Th1 T-helper cells?

Answer 8

IL-12

T-bet

Question 9

What is the product of Th1 T-helper cell and what effect does this have?

Answer 9

IFN-gamma (+ IL-12)

Activates macrophages

Question 10

During B-cell activation, which cell is presenting antigen?

Answer 10

The B-cell; T-cells cannot present antigen

Question 11

Describe the Th2 T-helper cell response.

Answer 11

Non-inflammatory

Change macrophages to promote tissue repair

Directs barrier immunity

IL-13 induces goblet cell production of mucus

IL-5 recruits eosinophils

Question 12

What is the polarising cytokine responsible for Th2 T-helper cells?

Answer 12

IL-4

Question 13

How do CD8+ cytotoxic T-cells cause cell death?

Answer 13

Perforins + granzymes

Question 14

What else must be bound to a dendritic cell to activate CD8+ cytotoxic T-cells?

Answer 14

CD4+ T-Helper cell

Upregulates co-stimulatory molecules on surface of CD8+ cytotoxic T-cells and secretes IL-2 to facilitate CD8+ cytotoxic T-cell proliferation

Question 15

Why is cross presentation necessary on dendritic cells?

Answer 15

So CD8+ cytotoxic T-cells can be activated.

Dendrites must bind CD8+ cytotoxic T-cell and CD4+ T-helper cell at the same time for CD8+ cytotoxic T-cell to be activated.

Question 16

What do MHC I presenting cells bind to in the lymph node?

Answer 16

CD8+ cytotoxic T-cells

Question 17

Name 3 unique components of the mycobacteria tuberculosis cell wall.

Answer 17

Mycolic acid (hydrophobic lipid shell)

Cord factor (toxic to mammalian cells)

Wax-d

Question 18

Why does TB infection require prolonged exposure?

Answer 18

A large number of bacteria are needed to establish and infection.

Cilia + mucus (mucociliary escalator) clears a majority of the bacteria from the upper respiratory tract, preventing the bacteria from infecting macrophages in the lower respiratory tract.

Question 19

How does mycobacteria tuberculosis stop phagocytosis by macrophages?

Answer 19

Blocks lysosomes formation

Question 20

What happens to macrophages after prolonged exposure to TNF-alpha?

Answer 20

They turn into epitheloid macrophages or foam cells

Question 21

Is a primary granuloma tight or loose?

Answer 21

Loose

Question 22

How does mycobacteria tuberculosis ensure being phagocytosed by macrophages?

Answer 22

Coats itself in C3b and mannose

Question 23

What is the effect of TNF-gamma on macrophages?

Answer 23

They turn into giant cells or increase their secretion of NOS and reactive O2 species

Question 24

What is unique about a secondary granuloma in a mycobacteria tuberculosis infection?

Answer 24

Caseating necrosis

Question 25

What happens in Post-primary TB infections?

Answer 25

Patients are immunicompetant so there is an overly strong, rapid immune response by activates macrophages. This causes cell death in the lungs and an ulcerative cavity.

There is no spread to lymphatics and no granuloma formation.

Question 26

How does the dendritic cell know to go to the lymph node?

Answer 26

Binding of antigen on MHCII changes chemokine receptors on dendrite

Question 27

Define a competitive enzyme inhibitor.

Answer 27

Competes for initial binding to the enzyme; other substrates can bind before it

Question 28

Define “reversible” in the context of enzyme inhibition.

Answer 28

The substrate can be removed from the enzyme receptor by another substrate

Question 29

Give a common example of a non-competitive, irreversible enzyme inhibitor.

Answer 29

Paracetamol

Question 30

What are the 4 components of MacConkey no.3 agar?

Answer 30

Lactose

Bile salts

Gram’s crystal violet

Neutral red dye

Question 31

What is MacConkey agar selective for? What is it differential for?

Answer 31

Selective for Gram negative bacteria (only Gram negative grow)

Differential for lactose utilisers (lactose utilisation turns agar pink)

Question 32

What colour indicates a positive oxidase test?

Answer 32

Dark blue

Question 33

What does a positive oxidase test rely on being present?

Answer 33

Cytochrome C oxidase

Question 34

Enterobacteriaceae are the most medically relevant bacteria. What 3 genera make up 95% of all clinical samples?

Answer 34

Proteus

Escherichia

Klebsiella

Question 35

In the oxidative/fermentative glucose test, what is type of bacteria is indicated by:

1. Oil tube and open tube both yellow
2. Oil tube yellow, open tube green
3. Oil tube green, open tube partially yellow at top

Answer 35

1. Facultative anaerobe
2. Obligate anaerobe
3. Obligate aerobe