L9-10 Flashcards
MHC class II location
extracellular
e.g. virus/ bacteria/ protozoa/ fungi/ worms
protection> Ig/ complement/ phagocytosis/ neutralization
interstitial spaces/ blood/ lymph
on APC’s
MHC class I location
intracellular
e.g. viruses/ protozoa
cytoplasmic
all nucleated cells
viruses
obligate intracellular parasites
innate defences> interferons/natural killer cells
T1 interferons
IFN alpha/ beta prevent viral nucleic acid production/ replication
NK cell receptors
target virally-infected host cells
potent > must be regulated
activate receptors on NK surface> recognise carb ligands
inhib receptors recognize class I
interferon mechanisms
- ^MX proteins
- ^MHC I expression
- ^ dendritic cells/ macrophages
- ^NK cells
- ^chemokines
interferon main pathway
virus-infected cell releases alpha/ beta
uninfected cell in vicinity binds and syntyhesises antiviral proteins
oligoadenylate synthetase degrade viral material via endocnuclease
protein kinase inhibits protein synthesis
NK cells
innate immune response
large granular lymphocytes
kill host cells infected w virus
from HSC
absence of Igs/ MHC
NK cell recognition
granzyme / perforin granules kill host cell
NK cell receptors
ACTIVATING> recog carb ligands/ triggers killing
INHIBITORY> recog MHCI, no binding
NK killing of infected cell mechanism
no inhibitory receptor action
- binds to ligand on activating receptor
- stimuli
- NK nuclear activation
- granzyme/ perforin release at interface between NK/ virally infected cell (apoptosis)
MHC 1 vs 2 binding peptide length comparison
MHC 1> binds shorter amino acids due to smaller groove 8-12 aa
MHC2> longer aa chain
cell-mediated specific immunity
CD8+ T cells recog MHC I
cytokines (w antiviral activity) > recog MHCII
2 mechanisms for apoptosis induction
- cytotoxic granule secretion (perforin/ granzymes)
- Fas ligand on T interacts w Fas on target
CD8 serial action
- many MHC1 presenting on host cells
- no inflammation
- targeted release of granzyme/ perforin
