B-VIII Microbes, immunity, evasion Flashcards
What are the general stages of bacterial infection
- Entry
- Colonization
- Proliferation
- Invasion
- Avoidance
What are some virulence factors?
Pili that can adhere to host tissue, capsules that protect against host defenses, different toxins, siderophores that promote iron uptake
How do defensins work?
They are cationic, which cause them to adhere to the bacterial membrane and form pores.
What are some immune responses against extracellular bacteria?
AMPs, complement system, phagocytosis. Immunoglobulins mainly, but some cell-mediated responses as well.
How can extracellular bacteria evade immune responses?
- Produce biofilm; protects against abs, complement, phagocytosis. Shields the MAMPs
- Antigenic variation to protect against recognition
- Inhibition of complement pathways in many different ways
How does Sbi inhibit the complement system?
Stops the alternative pathway by inhibiting the formation of C3a
How does SCIN inhibit the complement system?
Blocks C3 convertase which prevents progression
How does CHIPS inhibit the complement system?
Blocks the C5a receptor on the phagocytes
What are some immune responses against intracellular bacteria?
NK-cells, phagocytes, cell-mediated immunity
How can intracellular bacteria evade immune responses?
Antigenic variation, survival within phagolysosome, escape from phagosome
What are some immune responses against viruses?
NK-cells and mediated killing, IFN-type-I (inhibits viral replication), antibodies can block viruses from entering cells, CD8+ cells can kill virus infecting cells
How can viruses evade the immune system?
Antigenic variations, inhibition of Class I MHC, make the cell release immunosuppressive cytokines, kill or inactivate immunocompetent cells
What are some immune responses against parasites?
Phagocytosis mainly, Th2 responses
How can parasites evade the immune responses?
Can replicate within macrophage, induce polyclonal activation so that the antibodies will be “watered down”. Can also alter surface proteins
What are some factors that can influence a host’s ability to mount an immune response?
Age, the number of times the body has encountered the pathogen, and conditions like immunodeficiency (AIDS).
What is a key general feature of host-pathogen interactions regarding damage and disease?
Often, the damage and disease are caused by the host’s immune response rather than the pathogen itself.
True or false. Pathogens always cause damage to the host directly through mechanisms like toxins.
False; its often the hosts immune response that cause damage.
True or false. All bacteria use all the stages of pathogenesis, from entry to transmission.
False; the stages are more a general guideline
True or false. Capsules on bacteria primarily function to help them adhere to host tissues.
False; capsules function as a protection against host defenses
True or false. The main role of IFN-γ produced by NK cells during intracellular bacterial infections is to directly kill the bacteria.
False. IFN-gamma signals to macrophages to kill the bacteria.
