week 12 Flashcards
Which of the following BEST describes how Bacteroides fragilis polysaccharide A (PSA) promotes an anti-inflammatory response?
A) It directly kills pro-inflammatory gut bacteria, reducing inflammation.
B) It is recognized by TLR4, which activates pro-inflammatory pathways.
C) It is taken up by dendritic cells, which then induce Treg cell differentiation.
D) It blocks antigen presentation to prevent immune activation.
PSA is processed by dendritic cells, which stimulate Treg cells to secrete anti-inflammatory cytokines.
c
what is the difference of a mutualist and a pathogen?
mutualists release IL-10 cytokine to the dendritic cell causing the dendritic cells to give otu a weak signal to T-cells, giving an anti-inflammatory response
pathogens on the other hand cause the dendritic cells to release a lot of cytokines, which causes other immune cells to migrate to the area, which causes inflammation
How does Neisseria gonorrhoeae use Opa proteins during infection?
A) Opa binds to host receptors, enabling bacterial adhesion to mucosal epithelial cells.
B) Opa proteins secrete toxins that destroy epithelial barriers.
C) Opa proteins function as enzymes to break down host cell membranes.
D) Opa disrupts neutrophil chemotaxis, preventing immune detection.
Opa binds to host receptors, enabling bacterial adhesion to mucosal epithelial cells.
Why is the gut microbiome important for immune system regulation?
A) It provides a physical barrier that prevents pathogen invasion.
B) It educates immune cells to distinguish between harmful and beneficial microbes.
C) It directly destroys invading pathogens through phagocytosis.
D) It secretes histamines that trigger inflammation and immune responses.
The gut microbiome plays a key role in training the immune system to tolerate beneficial bacteria while responding to pathogens.
b
What is the MAIN function of Lipooligosaccharides (LOS) in Neisseria gonorrhoeae?
A) It triggers an inflammatory response by activating TLR4.
B) It helps bacteria adhere to host cells by binding to the asialoglycoprotein receptor (ASGPR).
C) It prevents phagocytosis by blocking antigen presentation.
D) It secretes toxins that lyse red blood cells.
– LOS mediates adhesion to host asialoglycoprotein receptors, specificallt on sperm, allowing N. gonorrhoeae to stick to mucosal surfaces.
b
Which of the following bacterial mechanisms involves a Type 3 secretion system that injects effector proteins to alter host cell structure?
A) Zipper mechanism
B) Trigger mechanism
C) Capsule formation
D) Superantigen toxin release
trigger mechanism
What is the MAIN difference between AB toxins and cytolytic toxins?
A) AB toxins work intracellularly, while cytolytic toxins disrupt membranes externally.
B) AB toxins disrupt cell membranes, while cytolytic toxins inactivate enzymes.
C) AB toxins only target immune cells, while cytolytic toxins target all cell types.
D) AB toxins bind to lipids, while cytolytic toxins target nucleic acids.
AB toxins work intracellularly, while cytolytic toxins disrupt membranes externally.
AB toxins have an A subunit and a B subunit. B unit helps adhesion to host and transports A across the cell membrane. A subunit has enzymatic activity
cytolytic toxins causes cells to lyse and disrupts membranes
How does Mycobacterium tuberculosis evade the immune system?
A) It secretes a superantigen that overactivates T cells.
B) It hides inside alveolar macrophages, preventing immune detection.
C) It produces hyaluronidase to degrade epithelial junctions.
D) It constantly changes its LPS structure to avoid TLR4 detection.
M. tuberculosis survives inside macrophages, making it hard for the immune system to eliminate it.
Which of the following correctly describes the impact of the gut microbiome on the central nervous system (CNS)?
A) Germ-free mice colonized with Lactobacillus rhamnosus show increased anxiety due to excessive neurotransmitter signaling.
B) Dysbiosis in the gut microbiome has been linked to neurological disorders such as autism and schizophrenia.
C) Gut bacteria only affect the immune system and have no role in brain function.
D) Stress has no effect on the gut microbiome’s composition.
B Dysbiosis in the gut microbiome has been linked to neurological disorders such as autism and schizophrenia.
a- mice acc show a decrease in anxiety
c- false
d- yes it does. stress causes a change in the bacteroides population and gives consequences for the cytokine release by immune and epithelial cells of the gut
What is a key characteristic of superantigen toxins?
A) They only activate a small, specific group of T cells.
B) They bind to host membranes and cause direct cell lysis.
C) They activate up to 20% of T cells, causing a massive immune response.
D) They block cytokine release, leading to immunosuppression.
Superantigens overactivate T cells, leading to excessive cytokine release and systemic inflammation.
What is the role of pattern recognition receptors (PRRs) in mammalian immunity?
A) They detect pathogen-associated molecular patterns (PAMPs) and initiate immune responses.
B) They destroy pathogens by directly lysing bacterial membranes.
C) They are secreted into the bloodstream to neutralize toxins.
D) They modify host DNA to increase resistance to bacterial infection.
– PRRs recognize PAMPs (like LPS, peptidoglycan) and trigger immune responses.
What is the key difference between PRRs and PAMPs?
A) PRRs are found on pathogens, while PAMPs are found on host immune cells.
B) PRRs detect molecular patterns associated with pathogens, while PAMPs are the molecular patterns themselves.
C) PRRs produce antimicrobial peptides, while PAMPs destroy bacterial membranes.
D) PRRs are secreted into the bloodstream, while PAMPs remain inside host cells.
PRRs (Pattern Recognition Receptors) are host receptors that recognize PAMPs (Pathogen-Associated Molecular Patterns), which are molecular signatures on pathogens.
How does IgA contribute to mammalian immunity?
A) It binds to pathogens in mucosal surfaces, preventing them from attaching to epithelial cells.
B) It triggers mast cell degranulation, causing an inflammatory response.
C) It functions as an opsonin, marking pathogens for phagocytosis.
D) It directly lyses bacterial cells by forming membrane attack complexes.
Answer: A – IgA is the primary mucosal antibody, preventing pathogens from adhering to epithelial cells in the gut, respiratory, and urogenital tracts.
lecture notes:
IgA binds to pathogens so they cannot bind on tje epithelial layer
- also form corsslinks with pathogens
What happens when the epithelial barrier is breached by pathogens?
phagocytes in the tissues secrete cytokines and chemokines (signalling molecules), which attract other immune cells to the site
what are the key differences in infection and disease?
infection is the growth of microorganisms on a host
disease is tissue damage due to infection
list the steps of infection
- adherance to the skin or mucosa
- invasion via epithelium
- multiplication of virulence factors and toxins
What is the key difference between exotoxins and endotoxins?
A) Exotoxins are secreted proteins, while endotoxins are components of the bacterial outer membrane.
B) Exotoxins only come from Gram-negative bacteria, while endotoxins are found in both Gram-positive and Gram-negative bacteria.
C) Exotoxins are heat-stable, while endotoxins are easily denatured by heat.
D) Exotoxins only cause local damage, while endotoxins are always systemic.
Exotoxins are actively secreted proteins, while endotoxins (like LPS) are part of the outer membrane of Gram-negative bacteria and are only released when the bacteria die.
What happens when TLR4 binds to lipopolysaccharide (LPS)?
binding causes a signalling cascade _> NFkB (transcription factor protein)->transcription of genes related to inflammation
