Infections And Immunity

Question 1

What are the features of acute inflammation?

Answer 1

• Resolve quickly
• Harmful stimuli removed
• Initial tissue destruction
• Followed by healing

Question 2

What are the features of chronic inflammation?

Answer 2

• Prolonged inflammation
• Harmful stimuli remain
• Simultaneous tissue destruction
  and healing
• Serious consequences

Question 3

What are infectious diseases?

Answer 3

Caused by diverse living agents that replicate in their hosts

Question 4

What is the determining factor for pathogenesis of infectious disease?

Answer 4

The interaction between host and micro-organism(s)

Question 5

What routes of entry into the host?

Answer 5

Respiratory

Skin

Swallowed

Congenital

Blood

Question 6

Is the route of entry important?

Answer 6

Does not necessarily correlate with the disease induced by a virus.

Some viral diseases were made localised others manifest in systemic symptoms.

Question 7

What is viral cytopathicity?

Answer 7

Damage or alterations to host cells caused by viral infection.

Question 8

What kinds of viral cytopathic effects are there?

Answer 8

Host protein synthesis shut off

Cell death

Cell fusion

Question 9

What are non-cytopathic virus?

Answer 9

Cause less obvious damage that can affect physiologic function of the cells

Question 10

What are the Initial Interactions Between Host and Virus?

Answer 10

Attachment

Entry

Uncoating

Replication

Assembly

Release

Question 11

What is attachment?

Answer 11

The virus attached to specific receptors on the surface of host cells.

Question 12

What is entry?

Answer 12

The virus gains entry into the host cell, either through direct fusion with the cell membrane (enveloped viruses) or receptor-mediated endocytosis.

Question 13

What is uncoating?

Answer 13

The viral genome is released from its protective capsid or envelope and enters the host cell’s cytoplasm or nucleus, depending on the virus type.

Question 14

What is replication?

Answer 14

The viral genome is replicated using the host cell’s machinery. This may involve transcription of viral genes to produce viral RNA or DNA, translation of viral proteins, and replication of viral nucleic acids.

Question 15

What is assembly?

Answer 15

Newly synthesized viral components are assembled into complete virions (virus particles) within the host cell.

Question 16

What is release?

Answer 16

Mature virions are released from the host cell, either by cell lysis, budding from the cell membrane (enveloped viruses), or exocytosis.

Question 17

What are the key features of innate immunity?

Answer 17

Pre-existing non-specific mechanism.

React rapidly

Can trigger other defensive mechanisms

Recruit immune cells

Question 18

What are the components of innate immunity?

Answer 18

Engulfing pathogens

Slow down pathogens replication

Bind to pathogen

Kill infected cells

Question 19

What types of cells engulf pathogens?

Answer 19

Macrophages

Monocytes

Neutrophils

Question 20

What kinds of cells in innate immunity kill cells?

Answer 20

Natural Killer (NK) cells

Question 21

What do CD8+ recognise?

Answer 21

MHC-I and 8-10 mer peptide via the T cell receptor

Question 22

How do CD8+(cytotoxic) cells kill infected cells?

Answer 22

Directly through perforin and FasL

Secrete antiviral cytokines

Question 23

What do CD4+ (helper) cells recognise?

Answer 23

MCH-II and 12-15 mer peptide via the T cell receptor

Question 24

What is the role of CD4+ (helper) cells?

Answer 24

Promote B-cell responses

Provide help to aid CD4+ T cell expansion.

Role of Tregs

Question 25

How are antibodies bound to the cells?

Answer 25

Initial secretion of IgM

Affinity maturation and antibody class switching to IgA

Question 26

Why is affinity maturation important?

Answer 26

Promote tighter binding to target antigen

Question 27

Where is IgG?

Answer 27

In serum

Question 28

Where is IgA?

Answer 28

A mucous membrane surface

Question 29

What is the role of antibodies?

Answer 29

Antibodies bind and neutralize free infective virus.

Antibodies could also bind to viral protein expressed on the cell surface.

Question 30

What is the purpose of the antibody binding to viral protein on cell surface?

Answer 30

Promotes the killing of infected cells via the complement attack and enhance phagocytosis via crosslinking Fc-receptor.

Question 31

What is protective immunity?

Answer 31

Immune memory

Question 32

Why is immune memory important?

Answer 32

Protect s from reinfection by the same pathogen

Question 33

What is the process of protective immunity?

Answer 33

Pathogen specific T- cells persist at a stable level.

Virus-specific B-cells persist.

Long lasting IgG in serum

Question 34

What are the viral immune evasions strategies?

Answer 34

• High replication rate and rapid evolution
• Modulation of cytokine responses
• Lack of immunogenicity
• Induction of Tolerance

Question 35

Why is high replication rate for viruses?

Answer 35

Ability to produce new virus particle and spread to new host before specific immune response.

Virus could overwhelm host immune system.

Question 36

Why is rapid evolution important for viruses?

Answer 36

No proofreading activity.

Immunological selection pressures select mutant good for survival.

Question 37

What is the CTL escape?

Answer 37

Mutations in T-cell epitopes can result in virus not being recognized by T-cells

Question 38

What is the antibody escape?

Answer 38

Evolution of surface proteins can allow re-infection of “immune” hosts

Question 39

What is Modulation or Hijacking of Cytokine Responses?

Answer 39

Modulation or hijacking of cytokine responses occurs when pathogens manipulate the host’s immune system, often leading to excessive inflammation or immune evasion.

This can result in severe complications, including cytokine storms.

Question 40

Define immunogenicity?

Answer 40

Ability of a substance to provoke an immune response in the body.

Question 41

What kinds of things reduce immunogenicity?

Answer 41

Reduction in amount of viral antigen presence

Infection in immune privileged sites

Prevents antigen presentation by infected cells

Question 42

Describe the down regulation of the MHC?

Answer 42

Disrupt the T-cell attack of infected cells by interfering antigen presentation

Cytomegalovirus protein US11 and US12 bind to MHC-I causing it to be retained in the ER.

US6 inhibits antigen transporter TAP prevents peptide loading onto MHC-I and downregulates MHC-I expression.

MHC-I deficient are NK targets

UL18 is a CMV homolog of MHC-I acting as a decoy for NK cells.

Question 43

What is clonal exhaustion?

Answer 43

Excessive amounts of viral antigen presented causing over-stimulation of TCR on T-cells results in peripheral deletion or anergy of virus specific T-cells.