Innate Immunity Flashcards
what are the resident cells that first respond to microbes that have breached the mucosal barrier?
macrophages
mast cells
dendritic cells
describe macrophages, mast cells, and dendritic cells
macrophages: engulf and destroy pathogens, clear dead tissue, produce cytokines
mast cells: ellicit immune response by secreting histamine, cytokines, and prostaglandins, and kill bacteria or inactivate microbial toxins using enzymes
dendritic cells: produce many kinds of cytokines that initiate inflammation and stimulate adaptive immunity by displaying antigens to lymphocytes
Gram (+) bacteria PAMPs
Nucleic acids: CpG moieties on DNA.
Proteins: pillin, flagellin
Cell wall lipids: lipoteichoic acid
Gram (-) bacteria PAMPs
Cell wall lipids: LPS
Bacterial capsule polysaccharides
Proteins: pillin, flagellin
Nucleic acids: CpG moieties on DNA.
Virus PAMPs
Nucleic acids: ssRNA, dsRNA, CpG moieties on DNA.
Fungi PAMPs
carbohydrate residues: mannam, glucans
DAMPs
damage associated molecular proteins
urate crystals, specific alarmins, heat-shock proteins
Toll-like receptor (TLR)
receptors on cell surfaces, recognize extrcellular microbial PAMPs
receptors also on endosome membrane and recognize nucleic acids released after microbes are digested
signal transcriptions factors for genes encoding immune response molecules
TLR 1
cell surface
bacterial lipopeptides
TLR 2
cell surface
bacterial lipopeptides and peptidoglycan
TLR 4
cell surface
LPS
TLR 5
cell surface
bacterial flagellin
TLR 6
cell surface
bacterial lipopeptides
TLR 3
endosome cell membrane
dsRNA
TLR 7
endosome cell membrane
ssRNA
TLR 8
endosome cell membrane
ssRNA
TLR 9
endosome cell membrane
CpG DNA
NF-kB
nuclear factor kB
transcription factor activated by TLRs
promote expression of chemical mediators of inflammation
NOD-like receptors
cytosolic receptors that sense PAMPs and DAMPs and stimulate immune response
NOD 1 and NOD 2
contain N-terminal CARD (capsase related domain)
sense bacterial cell wall peptidoglycans
activate NF-kB transcription factor
NLRP 3
sense many different microbial and pathologic changes in the cytosol
promotes production of cytokine IL-1B, forms inflammasome with capsase-1
RIG-like receptors
recognize RNA produced by viruses in the cytosol and activate signalling pathways that lead to production of type I interferons
lectin receptors
recognize carbohydrates - fungal glycans, mannose residues on fungi and bacteria
defensins and cathelicidins
peptide antibiotics produced by epithelial cells
INF-y
natural killer cell derived interferon-y
activates macrophages to kill phagocytosed microbes
classical macrophage activation
induced by innate immune signals - TLRs, and by IFN-y
involved in destroying microbes and stimulating inflammation
alternative macrophage activation
induced by IL-4 and IL-13
involved in tissue repair and stopping inflammation
innate lymphoid cells
lypmhocyte-like cells that do not have t cell antigen receptors, but produce cytokines and act like T lymphocytes
natural killer cells
sense infected and stressed cells and kill them via their granule proteins, which induce apoptosis in the infected cell
also secrete IFN-y, which activates macrophages to kill the associated microbes
how are healthy cells protected from detrustion by NK cells?
they have inhibitory receptors (MHC molecules) on their cell surface in addition to the activating receptors
which cells are the first-line innate response to viral infection?
natural killer cells: respond 5-7 days after intial exposure
how do NK cells get rid of the viral reservoir?
directly by releasing enzymes that induce apoptosis
or indirectly by producing IL12 - activating more NK cells, and IFN-y to activate macrophages and inhibit viral replication
what happens to recruited immune cells after immune response?
macrophages phagocytoes dead cells or they become pus if large numbers f cells were recruited
