Host defense Flashcards
bile destroys what type of virus?
enveloped viruses
innate immunity against viruses consists of what cell types / molecules?
interferon alpha and beta (type I interferon)
NK cells
macrophages
what is the other name of interferon type II?
IFNy
most viruses stimulate production of IFNa and IFNb by what type of host cells?
INFECTED host cells
how do IFNa and IFNb protect against viral infection?
inhibits viral replication in surrounding UNINFECTED hose cells
leukocytes produce which IFN?
alpha
what cell types produce INFb?
fibroblasts and other non-leukocytes
what cell types produce IFNa?
leukocytes
fibroblasts produce which IFN?
beta
once type I IFN binds to receptor, which two pathways can be taken? what is the end result?
- 2’-5’-oligoadenylate synthetase - degrades mRNA
- dsRNA-dependent protein kinase - inactivates eIF2
inhibition of protein synthesis and interruption of virus replication
what cell type is the first line of defense against virus-infected cells?
NK cells
viruses downregulate which class of MHC? why? which cell type is ‘released from inhibition’ in response to decreased MHC?
class I MHC avoid lysis by CTLs
NK cells
NK cell activity is enhanced by what compound?
IFN
ADCC
antibody dependent cell mediated cytotoxicity
what are the specific roles of NK cells (3)?
mediate ADCC
crosslinking of IgG Fc receptors
apoptosis and perforin mediated osmotic death
what are two antiviral products of macrophages? what do they do?
production of TNFa and NO - interfere with replication
which has a longer duration of humoral response to viral infection - serum or mucosa?
serum
what are the functions of antibodies (4)?
- prevent virus from binding target host cell
- opsonize virus to enhance phagocytosis
- activate complement to lyse viral envelopes
- facilitate ADCC by NK cells to lyse infected host cells
what cell type represents the principal protective immunity during ESTABLISHED virus infections?
CD8+ CTLs (adaptive cell mediated immunity)
is innate immunity effective against intracellular bacteria?
no
how are NK cells responsible for killing intracellular bacteria?
- NK cells activated by macrophage-produced IL-12
- NK cells then produce IFNy
- IFNy activates macrophages to become more efficient killers
what is required for full eradication of intracellular bacteria?
adaptive immunity
how does adaptive immunity deal with intracellular bacteria?
mediated by a DTH-like reaction
- T cells become activated - IFNy - activated macrophages eliminate bacteria
- some mycobacteria may persist in body for extended periods - granuloma formation
which IL steers immunity response toward Th2 immunity (antibody formation)?
IL-4
what is the mycobacterium strategy for evasion of immunity?
inhibits fusion of phagolysosome
what is the listeria monocytogenes strategy for evasion of immunity?
disrupts phagosome of macrophages and escapes into cytosol
what are the roles of IFN alpha and beta?
- induce resistance to viral replication in all cells
- increase MHC I expression and antigen presentation in all cells
- activate dendritic cells and macrophages
- activate NK cells to kill virus infected cells
how are bacteria that escape phagolysosomes into the cytosol killed?
bacterial peptides will be processed / expressed on class I MHC to activate CTLs
what type of immunity do you get with lepromatous leprosy?
Th 2 mediated (antibodies - but they are not very effective)
what type of immunity do you get with tuberculoid leprosy?
Th 1 mediated - granuloma formation
