Immunity to bacteria Flashcards
What are the four main mechanisms of antibacterial immunity?
Antibody production, phagocytosis, antimicrobial peptide AMP production, and coordination of adaptive immunity
What role do antibodies play in bacterial immunity?
They neutralize bacterial toxins, opsonize bacteria for phagocytosis, and activate the complement system
What is NETosis?
A process where neutrophils release their DNA and antimicrobial proteins to trap and kill bacteria
How do antimicrobial peptides AMPs contribute to immunity?
AMPs disrupt bacterial membranes and inhibit bacterial growth
What is the role of reactive oxygen species ROS and nitric oxide NO in immunity?
They are produced by phagocytes to kill bacteria during the respiratory burst
How do pneumococci evade phagocytosis?
They have a thick polysaccharide capsule that blocks complement binding
Why is antibody production critical for combating pneumococcal infections?
Pneumococci must be opsonized with antibodies for effective phagocytosis
What is the role of pneumolysin in Streptococcus pneumoniae infections?
Pneumolysin is a toxin that damages host cells and promotes inflammation
What are the primary sites of Streptococcus pneumoniae infections?
Nasopharynx (carriage), lungs (pneumonia), blood (sepsis), and meninges (meningitis)
How do bacterial pathogens modulate the host immune response?
By secreting toxins, modifying surface antigens, and inhibiting complement and phagocytosis
What is antigenic hypervariability?
Frequent changes in bacterial surface antigens to evade immune detection
What is the significance of IgA proteases in bacterial infections?
They degrade IgA, weakening mucosal immunity and allowing bacterial invasion
What are bacterial superantigens?
Molecules that non-specifically activate T cells, leading to massive cytokine release and immune dysregulation
How do bacteria block phagolysosome fusion?
By producing factors that inhibit the maturation of phagosomes, allowing bacterial survival in host cells
What are examples of Gram-positive bacterial pathogens?
Staphylococcus aureus, Streptococcus pneumoniae, and Clostridium difficile
What are examples of Gram-negative bacterial pathogens?
Escherichia coli, Salmonella, and Pseudomonas aeruginosa
How does bacterial LPS contribute to septic shock?
LPS activates TLR4, triggering excessive inflammation and systemic cytokine release
What are bacterial strategies to inhibit complement activation?
Production of proteases, surface capsules, and long-chain LPS to evade complement-mediated killing
What is the role of T regulatory cells in bacterial immunity?
Tregs help control excessive inflammation and prevent tissue damage during bacterial infections
What is the effect of pollution and inhaled sand on bacterial infections?
They increase bacterial carriage and virulence, reduce Treg activity, and promote inflammation
How does pneumococcal vaccination work?
Vaccines like PCV-13 induce antibody responses to prevent invasive disease and reduce nasopharyngeal carriage
What is the leading bacterial pathogen causing deaths in children under 5 years old?
Streptococcus pneumoniae, a leading vaccine-preventable cause of death
How does the immune system balance inflammation and bacterial clearance?
By regulating pro-inflammatory cytokines with anti-inflammatory cytokines like IL-10
What are the effects of pneumolysin on the immune response?
Pneumolysin depletes complement, activates the inflammasome, and reduces neutrophil killing
