evasion of immune defences

Question 1

How do herpes simplex and adenovirus evade immune detection through antigen presentation?

Answer 1

They inhibit MHC Class I antigen presentation, reducing recognition by cytotoxic T cells.

Question 2

What are examples of privileged sites for pathogen latency?

Answer 2

1.Herpes zoster virus: Latent in CNS (chickenpox -> shingles).
2.Echinococcus: Forms hydatid cysts in tissues (dog tapeworm).

Question 3

What is the cloak effect in immune evasion?

Answer 3

The uptake of host molecules by pathogens, such as Schistosomes, to disguise themselves from the immune system

Question 4

Name the four mechanisms of antigenic variation used by pathogens.

Answer 4

1.Large number of antigenic types.
2.Mutation (antigenic drift).
3.Recombination (antigenic shift).
4.Gene switching.

Question 5

How does Streptococcus pneumoniae evade the immune system?

Answer 5

Produces 91 capsular types to evade prior immune responses.
Its thick polysaccharide capsule resists phagocytosis.

Question 6

What are the two main vaccines for Streptococcus pneumoniae?

Answer 6

1.Pneumovax (23-valent polysaccharide vaccine): Effective in adults but weak in children.
2.Prevnar 13 (conjugate vaccine): Activates T-cell-dependent immunity.

Question 7

How does the conjugate vaccine (Prevnar 13) work?

Answer 7

B cells bind the polysaccharide linked to a toxoid.
T cells recognise peptides from the toxoid, boosting the antibody response to the polysaccharide.

Question 8

What are the surface antigens of the influenza virus?

Answer 8

Haemagglutinin and neuraminidase.

Question 9

Define antigenic drift and antigenic shift in influenza.

Answer 9

Antigenic drift: Small mutations in surface antigens.
Antigenic shift: Reassortment of genome segments between strains.

Question 10

How does Trypanosoma brucei evade the immune response?

Answer 10

It undergoes gene switching of Variant-Specific Glycoproteins (VSG), leading to recurring parasitaemia.

Question 11

What is the role of regulatory T cells in Helicobacter pylori infections?

Answer 11

They suppress TH1 and TH2 responses, allowing persistent infection.

Question 12

Name two diseases caused by Helicobacter pylori.

Answer 12

Gastric ulcers and gastric adenocarcinoma.

Question 13

How does Leishmania evade the immune system?

Answer 13

Hides within macrophages.
Increases regulatory T cells to suppress the immune response.

Question 14

What immune cells are targeted by the measles virus?

Answer 14

Dendritic cells, leading to decreased antigen presentation and IL-12 production.

Question 15

What immune disruption does the Ebola virus cause?

Answer 15

Suppresses dendritic cell function.
Triggers T-cell and NK-cell apoptosis.
Inhibits Type I interferon responses.

Question 16

How does Streptococcus pneumoniae neutralise antibodies?

Answer 16

It produces IgA protease to degrade mucosal antibodies.

Question 17

What is the role of vIL-10 produced by Epstein-Barr Virus?

Answer 17

vIL-10 downregulates the TH1 response, reducing immune effectiveness.

Question 18

Name a pathogen that inhibits complement activation.

Answer 18

Smallpox virus (vaccinia) produces molecules to block complement activation.

Question 19

What mechanism allows Mycobacterium tuberculosis to evade phagocytosis?

Answer 19

It survives and replicates within macrophages by inhibiting phagosome maturation.

Question 20

What is the effect of LPS on macrophages in innate immunity?

Answer 20

LPS triggers macrophages to secrete cytokines like IL-1 and TNF-α via TLR4, potentially causing cytokine storms.

Question 21

What immune response causes skin rashes in measles?

Answer 21

T-cell-mediated responses to the virus.

Question 22

How do antibodies against Streptococcus M protein cause rheumatic fever?

Answer 22

They cross-react with heart muscle antigens, leading to autoimmunity.

Question 23

What is a cytokine storm, and what role does it play in Ebola?

Answer 23

Overactivation of macrophages leads to massive cytokine release, causing vascular permeability and haemorrhage.

Question 24

What are the primary targets of Ebola’s shed glycoprotein?

Answer 24

Macrophages and dendritic cells, leading to cytokine release and coagulation issues.

Question 25

What type of pathogen causes African sleeping sickness?

Answer 25

Trypanosoma brucei, a protozoal parasite transmitted by the tsetse fly.

Question 26

: How does Pseudomonas evade complement?

Answer 26

Produces enzymes to degrade complement components like C3a and C5a.

Question 27

What is the primary immune cell targeted by HIV?

Answer 27

CD4+ T cells, along with macrophages and dendritic cells.

Question 28

What role do dendritic cells play in immunity?

Answer 28

They act as antigen-presenting cells (via MHC I and II) and link innate and adaptive immunity.

Question 29

Name an immunopathological effect caused by TB.

Answer 29

Granuloma formation due to chronic macrophage activation.

Question 30

What is the fatal mechanism of disseminated intravascular coagulation in Ebola?

Answer 30

Tissue factor expressed by infected macrophages initiates the coagulation cascade, leading to widespread clotting and organ failure.