CMB2004/L09 Immunity Against Infection II

Question 1

What are the protective immunities against organisms in interstitial spaces?

Answer 1

Antibodies
Complement
Phagocytosis
Neutralisation

Question 2

What are the protective immunities against organisms on epithelial surfaces?

Answer 2

Antibodies, especially IgA
Antimicrobial peptides

Question 3

Give 2 protective immunities against cytoplasmic organisms.

Answer 3

Cytotoxic T cells
NK cells

Question 4

Give 2 protective immunities against vesicular organisms.

Answer 4

T cell and NK-cell dependent macrophage activation

Question 5

Give 2 innate defences against viruses.

Answer 5

Interferons
NK cells

Question 6

Which type I interferons are released in virus-infected host cells?

Answer 6

IFN-a
IFN-B

Question 7

Describe the series of events that occurs upon release of IFN-a and IFN-B in response to viral infection. (5)

Answer 7

Induce resistance to viral replication by inducing Mx proteins, 2’-5’-linked adenosine oligomers and kinase PKR
Increase MHC class I expression and antigen presentation in all cells
Activate dendritic cells and macrophages
Activate NK cells
Induce chemokines to recruit lymphocytes

Question 8

How does IFN trigger degradation of viral mRNA? (4)

Answer 8

Induces synthesis of 2’-5’ oligoadenylate synthetase
Adenine trinucleotide synthesised
Activates endonuclease
Degrades viral mRNA

Question 9

How does IFN inhibit protein synthesis? (3)

Answer 9

Induces synthesis of protein kinase
Phosphorylation and inactivation of eIF-2
Inhibits protein synthesis

Question 10

Give a type II interferon and explain its effects.

Answer 10

IFNy secreted by T cells and NK cells
Inhibits TH2 response
Promotes TH1
Recruits macrophages

Question 11

rIFNa can be used to treat which diseases? (2)

Answer 11

Some cancers
Hepatitis B and C

Question 12

Describe natural killer (NK) cells.

Answer 12

Innate lymphoid cell
Large granular lymphocytes
Recognise structures of viral infected cells
Can recognise stressed cells in absence of Igs and MHC
Kill by extracellular mechanism - perforin and granzyme

Question 13

What is the role of:
a) activating receptors
b) inhibitory receptors?

Answer 13

a) Recognise carbohydrate ligands, triggers killing
b) recognises MHC class I molecules (no binding, only TCRs can do this)

Question 14

How are normal cells protected from NK cells? (2)

Answer 14

MHC class I on normal cells recognised by inhibitory receptors that inhibit signals from activating receptors
NK cell does not kill normal cells

Question 15

Explain how NK cells are triggered to elicit a response. (3)

Answer 15

Missing or absent MHC class I cannot stimulate a negative signal
NK cell triggered by signals from activating receptors
Activated NK cell releases granule contents inducing apoptosis in target cell

Question 16

Give the 2 components of cell-mediated specific immunity.

Answer 16

Cytotoxic T cells recognise viral peptide + MHC class I
Cytokines with anti-viral activity e.g., IFNy

Question 17

Describe the 2 mechanisms of cytotoxic T cells inducing apoptosis in the target.

Answer 17

Secretion of cytotoxic granules which polymerise in membrane and granzymes enter cell
Fas ligand on T cell interacts with Fas on target

Question 18

Describe the mechanism of inducing apoptosis by cytotoxic T cells. (3)

Answer 18

Collision and nonspecific adhesion
Specific recognition redistributes cyto-skeleton and cytoplasmic components of T cell
Release of granules at site of cell contact

Question 19

Explain the mechanism by which CTLs work. (4)

Answer 19

CTL recognises and binds virus-infected cell
CTL programs target for death, inducing DNA fragmentation
CTL migrates to new target
Target cell dies by apoptosis

Question 20

Give 3 functions of IFNy.

Answer 20

Inhibits viral replication
Upregulates MHC class I and II expression and antigen presentation
Increases macrophage phagocytosis of dead cells
Promotes NK cell killing activity

Question 21

Describe antibody and cell-mediated immunity in influenza. (2)

Answer 21

Infection induces antibody and cytotoxic T cell response
Antibody recognises viral haemagglutinin and neuraminidase
High CTL activity correlates with reduced viral shedding
Epidemics arise due to new strains not recognised by antibody

Question 22

Describe specific immunity against HIV. (2)

Answer 22

Attacks specific immune system
Targets CD4 T cell, macrophages and dendritic cells
Progressive development of AIDS leads to opportunistic infections

Question 23

Describe the relationship between CTL activity and HIV disease progression.

Answer 23

Higher levels of CTL activity show slower disease progression
Virus mutations that escape CTL recognition may lead to progression to AIDS

Question 24

Describe the immune response to SARS-CoV-2.

Answer 24

Dampens anti-viral type I interferon - aids viral replication
Viral proteins inhibit RIG1 (PRR)
Viral proteins stimulate NFkB activation - proinflammatory
Antibodies protective and role of cytotoxic T cells

Question 25

How can the body protect against parasites?

Answer 25

Opsonisation
Complement lysis
ADCC (antibody-dependent cell-mediated cytotoxicity)

Question 26

Which antibody response is strongly triggered by helminths?

Answer 26

IgE

Question 27

What is the role of the antibody response against helminths?

Answer 27

Mast cell mediated inflammation
Eosinophil ADCC

Question 28

Give an example of T cell immunity to Leishmania.

Answer 28

C57BL/6 mice resolve infection
BALB/c mice: fatal progressive disease

Question 29

Describe the C57BL/6 mouse response to:
a) IFN-y
b) IL-4.

Answer 29

a) +++
b) -

Question 30

Describe the BALB/c mouse response to:
a) IFN-y
b) IL-4.

Answer 30

a) -
b) ++

Question 31

Give 2 different effector mechanisms against malaria.

Answer 31

Sporozoite and merozoite susceptible to antibody
Antibody kills infected RBC
Cytotoxic T cells active against infected liver cells