Immunity to Bacteria Flashcards
To induce disease, a pathogen must be able to:
Have access to host Adhere to and colonize or invade host Evade host defense mechanisms Replicate on or within host Be directly or indirectly capable of causing damage to host cells or tissues
Non-specific immunity to bacteria
Skin/epithelial barriers Resident microflora Low pH (stomach, skin) Flushing action (lungs, urogenital tract, eyes, mouth) Lysozyme, lactoferrin, defensins Phagocytic cells Complement proteins
Microbial molecules activate immune system by binding to what?
Toll-like receptors
Specific immunity to bacteria
Neutralization of toxins or enzymes by antibodies
Indirect killing of bacteria by antibodies, complement, lysozymes
Opsonization of bacteria by antibodies and destruction by phagocytosis
Direct killing of bacteria through cytokine-mediated macrophage activation, antibody dependent cellular cytotoxicity, and T cytotoxic cells
Bacterial evasion mechanism: secretion of repellents/toxins
Inhibit movement of phagocytes
Bacterial evasion mechanism: capsules/outer coats
Inhibit attachment by phagocyte
Bacterial evasion mechanism: factors
Block killing mechanisms
Bacterial evasion mechanism: catalase
Breaks down hydrogen peroxide that would kill bacteria
Bacterial evasion mechanism: infecting cells
Infected cells lose their ability to present antigen
Bacterial evasion mechanism: escape from phagosome
Some bacteria such as M. leprae can escape from phagosome and multiply in cytoplasm
Final bacterial evasion mechanism
Killing phagocyte
Cell mediated cytotoxicity: mediators and result
Mediators: T cytotoxic cells, NK cells
Result: lysis of bacterial cell
4 mediators of bacterial cell lysis
T cytotoxic cells
NK cells
Complement
Lysozyme
2 mediators of bacterial opsonization
Complement
Antibodies
T helper cell role in bacterial immunity
Activation of macrophages, which phagocytose bacteria
