MHC Flashcards
what do extracellular PAMPs trigger?
PRR to (capture, process & present - APC) to MHC II cells
what does MHC II lead to?
humoral immunity (antibodies - circulating, compliment)
what are examples of extracellular PAMPs?
parasite, worms, fungi, bacteria
what are examples of intracellular PAMPs?
virus, protozoa, bacteria
what does intracellular PAMPs trigger?
MHC I, CD4+ T cells
what does MHC II, CD4+ T cells lead to?
cell-dependent immunity (antibodies, complement, macrophage)
what is the difference between cell-dependent immunity (MHC II) and humoral immunity (CD8+)?
cell-dependent has macrophage involvement
where are MHC I found?
all nucleated cells
where is MHC II found?
dendritic cells (blood, mucous membranes, lymph nodes), macrophage, B cells
how do the antigen proteins enter the cell in MHC I (intracellular)?
pathogen makes own proteins in cells (endogenous proteins)
bacterial endogenous protein enters host cell and goes to proteosome (degrades bacterial protein into fragments) - 10-15AA
what happens to the small bacterial proteins in MHC I (after interaction with proteosome)?
enter the RER (via TAP transporters), where the bacterial protein is broken down even more (8-10AA)
where are MHC1 proteins made within the cell?
by ribosomes in RER
how does MHC 1 interact with small bacterial proteins?
MHC1 has peptide binding cleft (variable region) - temp covered
MHC1 chaperoned to TAP transporter (where bacterial protein broken down further)
MHC1 interacts with small bacterial peptide fragment (via peptide binding cleft) - unique, specific
what happens after MHC1 and small bacterial protein interaction if they are complimentary?
complex leaves RER via endosome –> golgi apparatus –> exocytosis, to be presented on cell surface (APC)
what happens after the complex is presented on cell surface (APC)?
wait for interaction with CD8+ T cell - specific interaction
if complimentary, then can trigger cell-dependent immunity (macrophage, antibodies, complement
what can intracellular PAMPs trigger?
MHC I via CD8+ T cells, but also MHC II –> cytotoxic T cells, release cytokines to kill infected cells
what is special about an (MHC) APC cell?
can present lots of antigen peptide son 1 APC to interact with many MHC (specific)
how does an extracellular PAMP enter the cell?
MHC II, CD4+ T cells (bacteria, fungi, parasites, worms)
pathogen in ECF circulating, recognised by macrophage
macrophage engulf via phagocytosis
what happens after the macrophage has engulfed an extracellular PAMP?
lysosomes inside the cell (acidic environment) fuse with phagosome (bacterial engulfed)
form phagolysosome
acidic environment breaks down bacterial peptide (antigens)
how is MHC II produced? where?
within the RER, ribosomes synthesising MHC II, chaperoned out of RER (by li), through golgi, form new endosome (slightly acidic)
(CLIP prevents antigens binding to peptide binding cleft - variable region)
what happens after the lysosome has broken down the phagolysosome via acidic environment?
phagolysosome containing bacterial antigen fuse with MHC II - bind to peptide binding cleft (specific)
what happens if the MHC II binds to phagolysosome?
the macrophage (APC) now presents the MHC II + antigen (complex) on it’s cell surface, awaiting interaction with CD4+ T cells (APC to be activated)
what happens when a complimentary CD4+ cell interacts with MHC II?
the CD4+ T cell becomes T helper cell
promotes immunity by activating B cells
what do CD4+ T cells and CD8+ T cells go onto become?
CD4+: T helper (activate B cells - immunity) - MHC II (extracellular)
CD8+: T killer (release cytokines, kill infected cells) - MHC I (intracellular)
