evasion of immune defences Flashcards
lecture 10
How do herpes simplex and adenovirus evade immune detection through antigen presentation?
They inhibit MHC Class I antigen presentation, reducing recognition by cytotoxic T cells.
What are examples of privileged sites for pathogen latency?
1.Herpes zoster virus: inactive in CNS (chickenpox -> shingles).
2.Echinococcus: Forms hydatid cysts in tissues (dog tapeworm).
What is the cloak effect in immune evasion?
The uptake of host molecules by pathogens, such as Schistosomes, to disguise themselves from the immune system
Name the four mechanisms of antigenic variation used by pathogens.
1.Large number of antigenic types.
2.Mutation (antigenic drift).
3.Recombination (antigenic shift).
4.Gene switching.
How does Streptococcus pneumoniae evade the immune system?
Produces 91 capsular types to evade prior immune responses.
Its thick polysaccharide capsule resists phagocytosis.
What are the two main vaccines for Streptococcus pneumoniae?
1.Pneumovax (23-valent polysaccharide vaccine): Effective in adults but weak in children.
2.Prevnar 13 (conjugate vaccine): Activates T-cell-dependent immunity.
How does the conjugate vaccine (Prevnar 13) work?
B cells bind the polysaccharide linked to a toxoid.
T cells recognise peptides from the toxoid, boosting the antibody response to the polysaccharide.
What are the surface antigens of the influenza virus?
Haemagglutinin and neuraminidase.
Define antigenic drift and antigenic shift in influenza.
Antigenic drift: Small mutations in surface antigens.
Antigenic shift: Reassortment of genome segments between strains.
How does Trypanosoma brucei evade the immune response?
It undergoes gene switching of Variant-Specific Glycoproteins (VSG), leading to recurring parasitaemia.
What is the role of regulatory T cells in Helicobacter pylori infections?
They suppress TH1 and TH2 responses, allowing persistent infection.
Name two diseases caused by Helicobacter pylori.
Gastric ulcers and gastric adenocarcinoma.
How does Leishmania evade the immune system?
Hides within macrophages.
Increases regulatory T cells to suppress the immune response.
What immune cells are targeted by the measles virus?
Dendritic cells, leading to decreased antigen presentation and IL-12 production.
What immune disruption does the Ebola virus cause?
Suppresses dendritic cell function.
Triggers T-cell and NK-cell apoptosis.
Inhibits Type I interferon responses.
How does Streptococcus pneumoniae neutralise antibodies?
It produces IgA protease to degrade mucosal antibodies.
What is the role of vIL-10 produced by Epstein-Barr Virus?
vIL-10 downregulates the TH1 response, reducing immune effectiveness.
Name a pathogen that inhibits complement activation.
Smallpox virus (vaccinia) produces molecules to block complement activation.
What mechanism allows Mycobacterium tuberculosis to evade phagocytosis?
It survives and replicates within macrophages by inhibiting phagosome maturation.
What is the effect of LPS on macrophages in innate immunity?
LPS triggers macrophages to secrete cytokines like IL-1 and TNF-α via TLR4, potentially causing cytokine storms.
What immune response causes skin rashes in measles?
T-cell-mediated responses to the virus.
How do antibodies against Streptococcus M protein cause rheumatic fever?
They cross-react with heart muscle antigens, leading to autoimmunity.
What is a cytokine storm, and what role does it play in Ebola?
Overactivation of macrophages leads to massive cytokine release, causing vascular permeability and haemorrhage.
What are the primary targets of Ebola’s shed glycoprotein?
Macrophages and dendritic cells, leading to cytokine release and coagulation issues.
What type of pathogen causes African sleeping sickness?
Trypanosoma brucei, a protozoal parasite transmitted by the tsetse fly.
: How does Pseudomonas evade complement?
Produces enzymes to degrade complement components like C3a and C5a.
What is the primary immune cell targeted by HIV?
CD4+ T cells, along with macrophages and dendritic cells.
What role do dendritic cells play in immunity?
They act as antigen-presenting cells (via MHC I and II) and link innate and adaptive immunity.
Name an immunopathological effect caused by TB.
Granuloma formation due to chronic macrophage activation.
What is the fatal mechanism of disseminated intravascular coagulation in Ebola?
Tissue factor expressed by infected macrophages initiates the coagulation cascade, leading to widespread clotting and organ failure.
