Intracellular immunity (year 2) Flashcards
intracellular invasion will lead to what type of antigen presentation?
MHC 1
what type of cells recognise antigen on MHC 1?
CD8 T cells
how quickly are interferons secreted?
quickly - within hours of infection
interferons have antiviral activity, what does this mean?
protect neighbouring cells from infection by binding/blocking viral receptors
what are the two types of interferons?
I and II
give examples of type I interferons
IFNalpha and IFNbeta
give examples of a type II interferon
IFNgamma
where ate type I interferons released from?
tissue cells such as fibroblasts
what do type I interferons do?
stimulate NK cell activity and secretion of IFNgamma
where are type II interferons secreted from?
secreted from activated T and NK cells
what is the function of type II interferons?
prevent viral growth by the induction of nitric oxide secretion
they also activate macrophages
what T helper cell response is crucial for removal of intracellular pathogens?
1
how do cytotoxic CD8 T cells kill cells with intracellular pathogens?
release cytotoxic granules containing granzymes and perforin which lead to a loss of membrane integrity, this process is non-specific
they are also able to cause apoptosis by using Fas ligand
how do the macrophages activated by Th1 cells cause cell death?
express nitric oxide and the oxygen radicals that cause host cell death
this is not MHC restricted or specific
what are NK cells recruited by that they also secrete?
IFNgamma
what do NK cells recognise on cells that determine if the host cell is destroyed?
recognise the base of MHC not the antigen
if MHC isn’t present then the cell is targeted for destruction
why do NK cells target host cells that don’t express MHC complexes?
it is common for viral infections to down regulate MHC expression on the surface
what are common ways viruses try to evade immune detection?
downregulating MHC expression
mutation
changing antigen shape
what are the four types of pathogenesis shown by viruses?
lytic - destruction of host cells
persistent - slow release of viral particles damaging cells
latent - delay between infection and symptoms appearing
transformation - form tumours
what are some adverse consequences to viral immunity?
excessive immune response leading to damage of infected/neighbouring cells
why do protozoal infections require both humeral and cell mediated immune responses?
they have two stages of their lifecycle including an extracellular and intracellular stage
what drives the humeral immune response and what does it aim to do?
Th2 and aims to control parasite numbers in blood/tissue
how do protozoa invade immunity?
resistant to complement survive inside phagocytes manipulate dendritic cells inhibit motility inhibit cytokine production
name the factors of bacterial pathogenesis
exotoxin, endotoxin, superantigen
describe exotoxins of bacteria
these are secreted by the bacteria and are extracellular, they are usually targeted by neutralising antibodies
name the two main endotoxins
LPS and lipid A
what are endotoxins?
these are toxins that are attached to bacteria
where is LPS found and how does it work?
gram negative bacteria
activates macrophages to release inflammatory cytokines leading to tissue degredation
how do lipid A work?
only toxic if it enters the bloodstream where it activated coagulation and causes sepsis
what are superantigens?
polyclonal T cell activators
how do superantigens work?
hyper stimulate the immune system causing fever and vomiting
they also lead to shock causing organ failure and circulatory collapse
what is immunopathy?
damage to infected and bystander tissue due to over stimulation of cytokine production and complement activation by endotoxins
