Lecture 11 Flashcards
what is CPE?
cytopathic effects
what are some cytopathic effects (CPE) or virus infection?
- inhibition of DNA, RNA, and protein synthesis (cytolytic viruses do this)
- damage to cell lysosomes, release of digestive enzymes
- alteration of plasma membranes (results in enhanced susceptibility to immune system)
- cytotoxic effect of accumulation virus proteins: cytoplasmic and nuclear inclusions
- introduction and inhibition of apoptosis
- transformation of host cell into malignant cell
Can immune cells kill virally infected cells?
yes
briefly describe T-cell receptors
can recognize the peptide that is presented on the cell surface, and if it does it with secrete molecules that cause the lysis of that cell
briefly describe antibodies
binds to surface of viral glycoproteins and can recruit complement components that, when activated by binding to the antibodies, can form a membrane attack complex and make a big hole/lyse the cell
briefly describe NK (natural killer) cells
can recognize when antibodies are bound to a cell recognizing the Fc portion through their Fc receptors.
they bind this and also release molecules that can locally lyse these infected cells
what are two major pathways that can lead to cell death?
apoptosis and necrosis
True or False: viruses can induce both apoptotic and necrotic pathways to kill cells
true
from a cellular perspective, is necrosis passive or regulated?
necrosis is a relatively passive process
from a cellular perspective, is apoptosis regulated or a passive process?
it is a highly regulated process
how can necrosis be induced?
can be induced by severe insults to a cell such as heating, cooling, extremes of pH and other physical and chemical trauma
what is the end result of necrosis?
- loss of membrane integrity and “spilling” of cell contents into the extracellular environment
- this is viewed as a danger signal by the immune system and generally elicits a robust inflammatory response
- this is important for initiating an adaptive response to infection, but can also lead to immunopathology
what is apoptosis and how is it accomplished?
- it is programmed cell death
- accomplished by a cascade of biochemical steps that culminates in cell fragmentation and eventual engulfment of these fragements by phagocytic cells
- can release toxic compounds (reactive oxygen species) good for eliminating bacteria but also starts inflammation
what is one clear distinguishing feature between apoptosis and necrosis?
unlike necrosis, cell membranes remain intact and a robust inflammatory response is not initiated by the host. apoptosis is a “natural” process used
is the following sentence an example of apoptosis or necrosis: during development to eliminate unwanted cells
apoptosus
what is necrosis?
it is the “forced” death of body cells due to some sort of trauma
how can apoptosis be used in terms of misbehaving cells in the body?
apoptosis can be used to eliminate misbehaving cells from the body (ex. those that have suffered serious dna damage or those that display signs of cell cycle deregulation)
what is the connection between viral infection and apoptotic responses?
- virus infection frequently induces an apoptotis response inside infected cells and many viruses have developed mechanisms to circumvent apoptosis
- under some circumstances viruses can also directly induce apoptosis in infected cells, here the timing is critical however
what must happen in order for a virus to persist in a host population? why?
- there must be a balance between the severity of disease caused by the virus and the ability of the host to clear the infection
- if the virus kills the host too effeciently it will quickly run out of new hosts and be unable to persist in the population
- but if the host clears the virus effeciently, the virus will be unable to persist in the host populations
- the immune system plays a critical role in this delicate balance
how quickly do innate immune responses occur?
occur within minutes to hours after exposure to the pathogen
