T-cell Immunity Flashcards
What must occur for a T cell to be activated?
The adaptive immune system is initiated when naive T cells recognize peptide-MHC complex on the sruface of APCs;
Upon TCR signaling, T cells are “activated” leading to effector T cells
Do effector T cells act on target cells, pathogens, or both?
Effector T cells act on target cells, not the pathogens themselves
What is the surface marker for Naive T cells vs Memory T cells?
Naive: CD45RA
Memory: CD45RO
Differentiate effector memory T cells from central memory T cells
Effector: rapidly mature into effector cells upon reactivation and enter inflamed tissues
Central memory: take longer than effector T cells in producing cytokines; they remain in the lymphoid tissue and circulate as naive T cells
What is the relative life-span of memory T cells?
Long-lived
What are three signals required for productive activation of T cells upon meeting its antigen?
1) Activation: TCR binds to antigen:MHC complex
2) Survival: B7: CD28 co-stimulation
3) Differentiation: Cytokine production by APCs drive naive T cell to differentiate and proliferate
CD40/CD40L is also present
How do activated T cells respond to IL-2 signaling?
Activated T cells express high affinity IL2Ralpha (CD25) and proliferate in response to IL2 in an autocrine fashion.
What is the main function of CD8+ cytotoxic T cells?
Kill virus-infected cells.
CTLs target viruses and some intracellular bacteria
What is the primary function of CD4+ Th1 cells?
Activation of infected macrophages. Provides help to B cells for antibody production.
Th1 cells target microbes that persist in macrophages and extracellular bacteria
What is the main role of CD4+ Th2 cells?
Provide help to B cells for antibody production, especially switching to IgE
Effective against helminth parasites
What is the main role of CD4+ Th17 cells?
Enhance neutrophil response, and promotes barrier integrity (skin and intestines)
Targets fungus
What is the main role of Thf cells?
B-cell help: isotype switching + antibody production
What is the main role of Treg cells?
Suppression of T-cell responses
Which cytokines drive the differentiation of naive T cells into Th1 cells? What transcription factor is responsible for the differentiation?
IFN gamma
IL12
Transcription factor: Tbet
What cytokines are produced by Th1 cells?
IFN gamma, IL2, LTalpha
What cytokine drives the differentiation of naive T cells into Th2 cells? What transcription factor promotes this differentiation?
IL4
Transcription Factor: GATA3
Which cytokines are produced by Th2 cells?
IL4, IL5, IL13
Which cytokines drive the differentiation of naive T cells into Th17 cells? What transcription factor promotes this differentiation?
TGFbeta, IL6, IL21, IL23
Transcription Factor: RORgammaT
Which cytokines are produced by Th17 cells?
IL17, IL21, IL22
Which cytokines drive the differentiation of naive T cells to Thf cells? What transcription factor promotes this differentiation?
IL6
Transcription Factor: BCL6
Which cytokines are produced by Thf cells?
IL6, IL10, IL21
Which transcription factor promotes the differentiation of naive T cells to Treg cells?
FOXP3
Which cytokines are produced by Treg cells?
TGFbeta and IL10
Type I immune response (regulated by Th1 cells) are effective against what pathogens?
Intracellular pathogens
Type II immune responses (regulated by Th2 cells) are effective against which type of pathogens?
Extracellular pathognes
iTreg cells are important for what process?
Immune tolerance/ regulation of immune response to self-antigens
Th17 cells are important for providing immunity to what?
The gut
Thf (T follicular helper cells) are important for what process related to B cells?
Thf cells aid in the formation of germinal centers and differentiation of B cells into memory B cells and plasma cells
What type of immune response is implicated in autoimmune diseases (e.g diabetes)
Th1 - type 1 response
What type of immune response is implicated in the immunopathology of allergies, asthma and dermatitis?
Th2 - type 2 response
what is the general definition of an interleukin?
IL’s are heterodimers produced by leukocytes for the purposes of communication between leukocytes
Where in the cell are TLRs found?
TLRs are present on both the cell surface membrane and the membrane of intracellular vesicles
Which MHC is upregulated in mature DCs?
MHC II
Which co-stimulatory molecules are upregulated in mature DCs?
CD80, CD86, CD40
Discuss the translocation of DCs following activation.
Mature DCs migrate to lymphoid tissues following the CCR7 chemokine so that it can present antigen to T cells
Which cytokines are upregulated in mature DCs?
IL12 and IL18
T cells not activated by DCs in the lymph node exit via what?
The cortical sinus
What happens to T cells that do encounter their antigen in the lymph node?
They proliferate and differentiate into effector T cells and then exit the lymph node
Which T cells are involved in cell mediated inflammation?
Th1 cells
WHich T cells are involved in delayed-type hypersensitivity?
Th1 cells
Which factor, secreted by activated APCs maintains and stabilizes the Th1 response?
IL18
What is the main characteristic of IFN gamma?
IFN gamma is a potent pro-inflammatory cytokine
IFN gamma is the signature cytokine of what type of T cell response?
Th1