Type IV HSRs Flashcards
What are delayed type IV HSRs?
contact/skin permeable antigen activates TH1 cells leading to activation of macrophages
Why are delayed type IV HSRs “delayed”?
requires the activation and recruitment of macrophages
What happens in the sensitization phase of delayed type IV HSRs?
recognition, processing, presentation by MHC II
T cell activation and expansion
T memory cells made
What are the 3 types of T memory cells?
central
effector
resident
Where are central T memory cells located?
circulation/SLT
Where are effector T memory cells located?
circulation/SLT and tissue
Where are resident T memory cell located?
peripheral tissue
CD45RA is expressed on what cells?
naive T cells
CD45RO is expressed on what cells?
all T memory cells
CCR7 is expressed on what cells?
naive T cells
central memory T cells
CD103 is expressed on what cells?
resident memory cells
Where are monocytes located?
blood
Where are macrophages located?
tissue
What happens in the effector phase of delayed type IV HSRs?
APC present and activate T memory cells = IFN-g and TNF production = macrophage/monocyte recruitment
What does IL-12 do in the DT4HSR inflammatory loop?
induces more TH1 cells
What does TNF do in the DT4HSR inflammatory loop?
macrophage activation and vascular permeability
What does IL-8 do in the DT4HSR inflammatory loop?
recruits neutrophils
What does CCL2 do in the DT4HSR inflammatory loop?
recruits monocytes
Chronic macrophage activation due to the inability to clear antigen results in __________
granulomas
What 2 things can induce granulomas formation?
silica
sutures
What cytokines play a critical role in formation of granulomas and tissue damage?
IFN-g
TNF
(macrophage recruitment and release iNOS)
TB skin test (mycobacterium) induce a pure _____ response
TH1
Delayed type IV HSR are TH___ mediated
TH1
Poison oak can be a TH___ mediated response but also a TH___
TH1
TH17
What are 2 ways CD8 cells can be activate by DCs?
- sequential activation
- cross presentation
What is sequential activation?
DC —CD4 T cell interaction increases B7 levels, then DC interacts/activates CD8 T cell
What is cross presentation of CD8 T cells?
DC—CD4 T cell interactions, then changes their antigen processing to present on MHC I which can activate CD8 T cells
(present extracellular antigen on MHC I)
What is it called in cross presentation when DC switches thier antigen processing to present on MHC I?
cytosolic diversion
TCR don’t just recognize the peptide they also recognize _______
MHC
What 2 things are special about NKT cells?
- expresses invariant TCR (no memory)
- senses glycolipids only
NKT cells recognize ____ presented by ____ on APCs
glycolipids
CD1d
NKT cells DO NOT recognize…
MHC–peptide complex
How does CD1a present lipids differently than how MHC presents peptides?
lipid is buried in CD1d and the A’ roof is what is recognized
What expresses CD1a?
LC DCs
What causes A’ roof to be blocked in CD1a?
healthy skin lipid head causes steric hinderance
In the interference model of CD1a, binding of TCR is soley based on _____ not _____
CD1a not ligand
What linkage in skin is abnormal in atopic dermatitis?
fillagrin
What are corneocytes?
keratinocytes without nucleus
Where are regular LC DCs located?
epidermis
When LC DCs sample a foreign lipid with its CD1a what T cell subset is produced?
TH17
How does the skin sense PPD from TB skin test?
injected directly into dermis by passing LC DCs and being sensed by dermal DCs and macrophages
Only CD1___ has an A’ roof
CD1a
What are 2 delayed type IV HSRs?
- PPD (TB skin test)
- urushiol (poison oak)
