Immunity to Viruses Flashcards
What are the types of cell death?
necrosis and apoptosis
What is apoptosis?
programmed cell death
What is the extrinsic pathway of apoptosis mediated by?
receptors
What receptors are involved in the extrinsic pathway of apoptosis?
Fas/FasL and TNF receptor/TNF
What is the intrinsic pathway of apoptosis?
it is a mitochondrial pathway and release of cytochrome C to initiate the caspase cascade
Which type of cell death is characterized by an inflammatory response?
necrosis
What type of cell death is organized?
apoptosis
What is the difference between what happens to the membrane in apoptosis and necrosis?
in apoptosis, the membrane blebs, in necrosis it degrades
What happens to the contents of the cytoplasm in necrosis?
the contents are released
What happens to the contents of the cytoplasm in apoptosis?
they are phagocytized and digested
What cells are involved in necrosis?
macrophages, neutrophils, eosinophils, and basophils
What cells are involved in apoptosis?
NK and CTL cells
What mechanisms do CTLs and NK use to kill target cells?
perforin and granzyme pathway, TNF receptor/signal for apoptosis, and Fas/FasL receptor mediated killing
How does the perforin and granzyme pathway work?
perforin creates a pore in the target cell, granzymes enteer the target cell and activate the intrinsic apoptotic pathway
How does the TNF receptor/signal activate killing target cells?
it is receptor mediated activation of the caspase cascade that leads to apoptosis
How does the Fas/Fas L receptor mediated killing work?
Fas/Fas L activates the extrinsic apoptotic pathway
What activates a NK cell to kill another cell?
absence of normal MHC I, binding to MICA molecules on the cell, antibody-dependent cell mediated cytotoxicity
If MHC I normally presents itself, why does NK not kill it?
because MHC I inhibits the killing effects of NK
What are MICA and MICB?
stress proteins
What does MICA and MICB do?
they inhibit the inhibitory power of MHC I which allows NK to kill it
How does antibody-dependent cell mediated toxicity work?
antibody coats the cell allowing NK to bind to the Fc receptor which then will induce apoptosis via perforin/granzyme
What is NK looking for mainly when it is trying to kill?
the presentation of MHC I; ‘Present yourself or DIE’
What is the timing of NK’s response?
rapid response; it is part of innate immunity
What does CTL need for it to facilitate its killing abilities?
MHC I to present the antigen
What is the timing for CTLs response?
it is part of adaptive immunity, so upon first encounter it takes from 7-10 days
Why would it be beneficial in the case of a viral infection for an organism to have both CTLs and NKs?
Because the virus is going to try and hide from the CTL so it will not express it’s MHC I, little does it know that the NK cell looks for lack of MHC I expression and it will kill the virus
What are some killing mechanisms of the immune system?
apoptosis, oxidative metabolism, defensins, macrophages, MAC, nitric oxide, netosis
What are two parts of the innate immune response that are important for protection against viruses?
interferons and NK cells
What are two parts of the adaptive immune response that are important for protection against viruses?
cytotoxic T cells and antibody
What are some important functions of antibodies?
neutralization, complement fization by classical pathway, antibody-dependent cell mediated cytotoxicity
What are type I interferons produced by?
virally infected cells
What is the function of type I interferons?
degrade viral RNA, inhibit virion assembly, increase MHC I presentation
What is the function of type II interferon (gamma)?
they activate macrophages, and release cytokines to tell B cells to make IgG
What type of immunity is associated with type II interferon?
adaptive immunity
What are some important properties of vaccines that would stimulate CTLs?
modified live vaccines, iscoms; gotta do something to get the peptides onto MHC I
What apoptotic pathway is perforin/granzyme involved in?
intrinsic
What apoptotic pathway is Fas/FasL part of?
extrinsic
What apoptotic pathway are stress enzymes part of?
intrinsic
