4 Cell Mediated Immunity (1 Hour) Flashcards
Where do T cells leave the lymph nodes through?
HEVs
What cell alone is capable of activating naive T cells?
Dendritic cells
What can activate memory T cells?
B cells and macrophages
What activates B cells and macrophages?
CD4+ T cells
What is CD25 also known as? What does it function in?
IL2r, autocrine growth signal
How are T cells trapped? Why are they?
Down regulation of chemokines that would cause the T cell to leave the node; they need to stay to activate B cells
In the T cell immune synapse, what is the function of the CD4/8 interaction with HLA?
Signal transduction
What is the function of the CD28 on T cells interacting with the CD80/B7 on APCs?
Costimulation
What two interactions hold T cells and APCs together?
LFA (T) -> ICAM1 (APC)
CD2 (T) -> LFA3 (APC)
What is often needed for CD8 T cell activation? Explain
Cross presentation
This is when you have Th cells costimulating DC with cytokines to get CD8 and you also get DC presenting antigen directly from APC to CD8
What differentiates a Th1? What TF is required?
IFNg and IL12, T-bet
What differentiates Th2? What TF is involved?
IL4, GATA-3
What differentiates Th17? What TF is involved?
TGFb, IL6, IL23; RORgT
What does Th1 produce?
IFNg and TNFa
What do Th1 activate?
Macrophages
What do Th2 activate?
Eosinophils and alternative macro
What do Th17 produce? What does this do?
IL17, 22
Activates neutro through IL17
Increased barrier function through IL22
Role in IBD, RA, MS
What do bacterial super antigens do? What do they bind to?
They activate T cells without co-stim
They act on the b portion of the TCR
An effector T cell is able to respond to antigen in the absence of
CD28(T)/CD80(DC) interaction
What 2 things do activated T cells start making?
Co stimulatory molecules (CD28) Also inhib (CTLA4) (binds to CD80 instead)
What happens during activation that allows T cells to respond to the site?
Integrins become high affinity
What increases HLA expression on CTL?
Type 1 IFNs
What does the Th1 make to stimulate CTL?
IL2
What is Fas also known as?
CD95
How does CTL kill a cell?
Perforin and granzymes
Or FasL binding to Fas on target
Why does CTL kill in clusters? What do they produce?
IFNa/b to slow viral replication and also increases MHC 1 on other cells
To ensure that the virus is cleared around the initial infected cell
How does NK kill?
Same way as CTL
What enhances NK killing
IFNa, IFNb, IL12
What cells act in Ab dependent cell-mediated cytotoxicity?
NK, macro, neutrophil, eosinophil
What causes CTL exhaustion
CTLA4 on T cell interacting with APC
What do memory T cells require for survival?
IL7 (BM and thymic stromal cells) and IL15 (Th2)
Why are memory responses faster?
Mem T cells can be activated w/o co-stim
What do Treg express? What TF is of interest?
CTLA4 and CD25 (IL2r)
FOXp3
How does EBV evade the immune system?
Shuts down proteosome
Produces IL10 to calm down macrophage
What does IFNg stimulate?
Activates macrophages (classical) Activates B cell to stim. complement binding Stim. class 2 HLA and CD80