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Immune Responses and Microbial Evasion
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Immune Responses and Microbial Evasion
Immune Responses and Microbial Evasion
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1
Question
What types of microbes are included in the introduction to immunity?
Page 2
Answer
Bacteria, viruses, fungi, and parasites.
2
Question
What determines the outcome of host-microbe interactions?
Page 2
Answer
The balance between host defensive mechanisms and microbial evasion.
3
Question
How does the immune response to pathogens vary?
Page 2
Answer
Depending on whether pathogens are extracellular or intracellular.
4
Question
What is the first step for circulating naive Th cells in response to antigens?
Page 2
Answer
Recognize their antigen.
5
Question
What happens after naive Th cells recognize their antigen?
Page 2
Answer
They differentiate into one of several effector-cell lineages depending on pathogen type and location.
6
Question
Which effector Th cell lineage targets extracellular fungi and bacteria according to Figure 1?
Page 2
Answer
Th17 cells producing IL-17.
7
Question
What immune components target intracellular bacteria and protozoa in Figure 1?
Page 2
Answer
Th1 cells producing IFN-γ and TNF, activating macrophages.
8
Question
Which cells are effectors against helminths in Figure 1?
Page 2
Answer
Th2 cells producing IL-4, IL-5, IL-13, eosinophils, basophils, and mast cells.
9
Question
How do extracellular bacteria primarily trigger innate immunity?
Page 3
Answer
Through neutrophils, complement pathways, and acute phase proteins.
10
Question
What adaptive mechanisms target extracellular bacteria?
Page 3
Answer
Antibody neutralization, IgG classical complement lysis, and Th1 inflammation.
11
Question
Why are innate responses often ineffective against intracellular bacteria?
Page 3
Answer
Because intracellular bacteria are difficult for host defenses to eliminate.
12
Question
What adaptive responses fight intracellular bacteria?
Page 3
Answer
Th1 producing TNF and IFN-γ, stimulating infected cells, and cell-mediated immunity.
13
Question
What innate immunity targets viruses?
Page 3
Answer
NK cells inducing IFN state to inhibit viral replication.
14
Question
What adaptive immunity eliminates viruses?
Page 3
Answer
Th1 producing IFN-γ and CD8 CTL.
15
Question
What innate mechanisms fight extracellular fungi?
Page 3
Answer
Neutrophils.
16
Question
What adaptive responses target extracellular fungi?
Page 3
Answer
Th17 producing IL-17 promoting neutrophils.
17
Question
What immune cells target helminths?
Page 3
Answer
Eosinophils, neutrophils, mast cells, and basophils.
18
Question
What is the first mechanism of microbial immune evasion?
Page 4
Answer
Antigenic variation involving frequent changes in surface antigens to escape recognition by antibodies and memory cells.
19
Question
How does antigenic variation allow chronic infections?
Page 4
Answer
By escaping recognition by antibodies and memory cells such as in influenza virus.
20
Question
What is the second microbial evasion mechanism?
Page 4
Answer
Inhibition of antigen presentation by blocking MHC class I or II pathways, preventing T cell recognition.
21
Question
Which viruses inhibit antigen presentation?
Page 4
Answer
CMV and herpes viruses by preventing T cell recognition.
22
Question
What prevents phagocytosis in microbial evasion?
Page 4
Answer
Production of capsules or surface proteins that prevent engulfment, such as in Streptococcus pneumoniae.
23
Question
How do microbes survive inside phagocytes?
Page 4
Answer
By inhibiting phagosome-lysosome fusion, resisting lysosomal enzymes, or escaping to cytosol.
24
Question
Name a microbe resisting lysosomal enzymes inside phagolysosome.
Page 4
Answer
Salmonella typhi.
25
Question
What is complement evasion mechanism?
Page 4
Answer
Expression of surface molecules that inhibit complement activation or promote degradation, e.g., Neisseria meningitidis.
26
Question
How do some microbes suppress immunity?
Page 4
Answer
Production of molecules that inhibit or kill immune cells, such as viral IL-10 homologs or toxins targeting leukocytes.
27
Question
What protective structure limits immune access in biofilms?
Page 4
Answer
Biofilm formation creates a barrier limiting immune cell and antibody access, e.g., Pseudomonas aeruginosa, Candida species.
28
Question
What clinical defect leads to intracellular infections like tuberculosis?
Page 5
Answer
Defect in Th1-MQ axis.
29
Question
What is required for effective immunity against intracellular bacteria like M. tuberculosis?
Page 5
Answer
IL-12-driven Th1 differentiation and IFN-γ-mediated macrophage activation.
30
Question
What happens with defects in Th1-MQ pathway?
Page 5
Answer
Leads to severe or disseminated TB.