Chapter 4: Periphery: Innate Immune Response Flashcards
What does IELs stand for? What is another name for it?
Intra-epithelial lymphocytes
γδ T cells
What are receptors of the innate immune system known as?
PRRs (pattern recognition receptors)
What do PRRs recognize?
PAMPs or DAMPs (damage-associated molecular patterns); released from dying or damaged cells
Where are inflammasomes expressed?
in myeloid cells (like macrophages, neutrophils, and dendritic cells)
Activation of inflammasomes results in the production of what inflammatory cytokines?
IL-1β and IL-18
What is the purpose of inflammasomes?
to activate caspase 1 and then cleave pro cytokines to their active forms
What are the extracellular TLRs?
TLR -1, 2, 4, 5, 6
Pathogen target of TLR 2?
Bacterial peptidoglycan
Pathogen target of TLR- 4?
LPS
Pathogen target of TLR-5?
flagellin
Which TLRs recognize bacterial lipopeptides?
TLR-1, 2, 6
What are the intracellular (endosomal) TLRs?
TLR-3, 7, 8, 9
What pathogen does TLR-3 recognize?
DS RNA
What pathogen does TLR- 7, 8 recognize?
SS RNA
What pathogen does TLR - 9 target?
unmethylated CpG oligonucleotides
What are the downstream effects of activation of TLRs?
activation of transcription factors (including NF-kB) which results in the transcription of cytokines, adhesion molecules, and enzymes that are antimicrobial
Where are NLRs located? What does it stand for?
NOD-like receptors; intracellular (cytosolic)
What are the NLRs?
List the types.
NOD1, NOD2, NLRP-3
NOD1, NOD2 pathogen target?
comoponents of bacterial PG
Downstream effects of NOD1, NOD2?
signals via NF-kB result in macrophage activation
NLRP-3 pathogen target.
microbial products and molecules from damaged or dying cells (ATP, uric acid crystals, reactive oxygen species)
Downstream effects of NLRP-3?
Inflammasome
NLRP- 3 (sensor) + adaptor protein links procaspase 1 and activates it to caspase 1; it is the caspase that cleaves the pro-IL-1B to generate IL-1B
RLR stands for what? Where is it located in the cell?
RIG-like receptors; cytoplasm
What is the receptor name of RIG-like receptors?
RIG-1, MDA-5
What is the pathogen target of RLR?
viral RNA
Downstream effects of RLR?
interferon production
Classical M1 pathway of macrophage development is activated by what factors?
TLRs, IFN-y
The alternative pathway of macrophage development is induced by what cytokines?
IL-4, IL-13
Classical M1 pathway of macrophage development purpose?
phagocytosis, initiate inflammatory response
Alternative M2 pathway of macrophage development purpose?
tissue repair and control of inflammation
What is the overall effect if there is a mutation in signaling molecules affecting TLRs?
recurrent, severe bacterial infections (pneumonia)
What is the overall effect of gain of function mutations in inflammasome?
- gout
- atherosclerosis
- type II diabetes
What is the effect associated with NOD-2 mutations?
IBD
What are some effects of mutations associated with IL-12 receptor deficiency and IFN-y receptor deficiency?
recurrent infections with intracellular bacteria (mycobacterium)
What CD marker is present on monocytes?
CD 14
What CD marker is present on macrophages?
CD 14
What CD marker is present on neutrophils?
CD 14
What cytokine released from macrophages and DCs activates NK cells?
IL-12
Name the complement anaphylatoxins.
C3a
C4a
C5a
Which complement is important for opsonization of pathogens?
C3b
Which complement proteins are responsible for putting holes in membranes of pathogens?
C5b - C9 MAC complex (MAC; membrane attack complex)
What organism is the MAC mainly good at killing?
Neisseria species
In addition to being an anaphylotoxin, what is another important function of C5a?
as a chemotactic factor
What are the 4 steps in the extravasation of phagocytes?
Step 1: Rolling
Step 2: Activation by chemo-attractants
Step: 3: Arrest and adhesion
Step 4: Transendothelial migration
Omphalitis
a swelling and reddening around the stalk of the umbilical cord
Name some major chemoattractive molecules.
IL-8,
complement split product C5a,
Leukotriene B4,
Formyl methionyl peptides
How do reactive nitrogen species play a role in intracellular killing of pathogens?
iNOS (inducible nitric oxide synthase) converts arginine to nitric oxide which has potent antimicrobial properties
Function of lysozyme?
digests bacterial cell walls by cleaving peptidoclycan
Defensins function?
form channels in bacterial cell membranes
What are the major pro-inflammatory cytokines responsible for producing an acute inflammatory response?
IL-1, IL-6, TNF-a
What is the major response of IL-1, TNF-a, and IL-6 on the liver?
acute-phase proteins, such as CRP, mannose-binding protein, and complement components
IFN-α/ β and NK cells are 2 major mechanisms for dealing with infections in the innate or adaptive immune response?
innate immune response
What is a major function of interferon?
acts on target cells to inhibit viral replication, not the virus
How does interferon inhibit viral protein synthesis?
- activation of an RNA endonuclease which digests viral RNA
- phosphorylation of protein kinase, which inactivates eIF2, inhibiting viral protein synthesis
Interferon-α has what important clinical applications?
well-known antiviral activity and has been used in the treatment of hepatitis B and C infections
Cancer therapy: hairy B-cell leukemia, chronic myelogenous leukemia, and Kaposi sarcoma
Interferon- β has what important clinical applications? Benefits?
MS
Patients enjoy longer periods of remission and reduced severity of relapses
Interferon-y has what important clinical applications?
being used in the treatment of chronic granulomatous disease (CGD).
What is the major function of IFN-y?
potent inducer of macrophage activation and a promotor of inflammatory responses
MOA IFN-y is used to treat CGD?
significantly reverse the CGD patients inability to generate toxic O2 metabolites inside phagocytic cells
How can the side effects of IFN-y treatment be mitigated?
acetaminophen
Another name for the marker CD16 found on NK cells?
FcRy
What are the 2 categories of receptor employed by NK cells?
(KAR) killer activating receptor
(KIR) killer inhibitory receptor
Overall explain how KIR and KARs work?
if only KARs are engaged, the target cells will be killed;
if both the KIRs and the KARs are ligated the target cell lives
Therefore the inhibitory signals trump the activation signals
What is the major KAR expressed by NK cells?
NKG2D
What are some major ligands that bind to KARs?
MIC glycoproteins
Where are MIC proteins found? Explain how KARs act once binding to them.
stress proteins that are expressed only when cells are infected or undergoing transformation
Upon binding of KAR to MIC, NK cells become cytotoxic, resulting in death of target cell
What is the MOA of KIRs?
activate protein tyrosine phosphatases which inhibit intracellular signaling and activation by removing tyrosine residues from various signaling molecules
KIRs on NK cell bind to a specialized type of MHC class I ag called HLA-E