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9.1 Immunity to Infection β Test 1
Q1. Immunity to extracellular bacteria depends mainly on:β Antibodies, complement and phagocytosis
Q2. Defence against intracellular bacteria (e.g. Mycobacterium tuberculosis) relies chiefly on:β Th1 cells activating macrophages via IFN-Ξ³
Q3. Antiviral defence is mediated principally by:β Cytotoxic T cells, NK cells and interferons (plus neutralising antibody)
Q4. Type I interferons (IFN-Ξ±/Ξ²) contribute to antiviral immunity by:β Inducing an antiviral state in neighbouring cells
Q5. Immunity to large parasites such as helminths is associated with:β IgE, eosinophils and mast cells (Th2 responses)
Q6. Antigenic variation, used by pathogens such as influenza and trypanosomes, helps them to:β Evade existing immune memory by changing surface antigens
Q7. Some intracellular pathogens evade immunity by:β Inhibiting MHC class I expression or escaping the phagosome
Q8. Mucosal surfaces are protected chiefly by:β Secretory IgA
Q9. Opsonisation aids clearance of encapsulated bacteria because the capsule:β Resists direct phagocytosis until coated by antibody/complement
Q10. The role of NK cells in viral infection is especially important when viruses:β Downregulate MHC class I to evade cytotoxic T cells
Q11. The acute-phase response during infection includes:β Fever and increased acute-phase proteins (e.g. CRP) driven by IL-1, IL-6 and TNF
Q12. Sterilising immunity refers to:β Immunity that completely prevents establishment of infection
Q13. Granuloma formation in chronic infection (e.g. tuberculosis) serves to:β Wall off and contain organisms that cannot be eliminated
Q14. Bacterial exotoxins are best neutralised by:β Antibodies (antitoxins)
Q15. A pathogen that survives inside macrophages by preventing phagosomeβlysosome fusion is exemplified by:β Mycobacterium tuberculosis
Q16. Why are individuals without a spleen at particular risk from encapsulated bacteria?β The spleen is key for clearing blood-borne encapsulated organisms and antibody responses
Q17. Complement contributes to antibacterial defence by all of the following EXCEPT:β Synthesising antibody
Q18. Cytotoxic T-cell killing of a virus-infected cell is advantageous because it:β Eliminates the cell before progeny virus can be produced
Q19. The immune response best suited to clear a toxin-mediated disease such as tetanus is:β Production (or transfer) of neutralising antitoxin antibody
Q20. Antigenic drift in influenza is caused by:β Point mutations in genes encoding surface epitopes
Q21. Which pathogen is well known for antigenic variation?β Influenza virus
Q22. Match each pathogen type with its principal protective mechanism and select the correct option.β A-ii, B-i, C-iv, D-iii