Effector functions of T cells Flashcards
Where are T cells produced?
Their progenitors are produced in the BM which then migrate and mature in the thymus via TCR recombination and tolerance selection. They leave the thymus as differentiated CD4 or CD8 cells searching for MHC.
What determines a T cells function?
Must bind with high affinity to proliferate and differentiate. The type and duration of a cytokine profile signal determines the function.
What are the subtypes of CD4 Th cells?
Th1
Th2
Th17
Treg
What do CD4 Th cells respond to?
MCH II extracellularly in response to viruses, bacteria, protozoa, fungi, worms
What do CD4 Th functions result in?
Complement cascade, phagocytosis and antibodies
What do cytotoxic CD8 cells respond to?
Intracellular MCH I in response to viruses and protozoa
What do cytotoxic CD8 functions result in?
NK and cytotoxic T cell activation
What are the three signals needed for T cell differentiation?
1st - binding of TCR to DC with good affinity
2nd - sufficient costimulation = proliferation
3rd - Cytokines and DC surface molecules drive downstream pathways to upregulate a specific lineage of TF for specific interleukin production.
What is the function of a CD8 T cell?
Activate macrophages for intracellular pathogen killing.
Contain cytotoxic granules of perforin and granzymes to mediate cell death.
Express Fas ligand to kill susceptible cells via apoptosis.
What stimulates a CD8 T cell?
MHC I on DC, CD4 Th cell or high conc of IL-2
What cytokines cause differentiation to Th1?
IL-12, IL-2 and their own effector cytokine IFNgamma
What TF controls transcription of the cytokines released by Th1 and what are they?
Tbet - TNFgamma and IL-2
What type of infections are Th1 cells important for and what immune cells do they activate?
Activate macrophages in response to intracellular bacteria in vacuoles. Involved in delayed hypersensitivity reactions and cytotoxic T cell activation.
What cytokines cause differentiation to Th2?
IL-4
What cytokines are released by Th2 and what TF controls it?
GATA-3 = IL-3, IL-4, IL-5, IL-10, IL-13
What type of infections are Th2 cells important for and what immune cells do they activate?
Promote B cell activation through class switching to IgE. Involved in allergic reactions and helminth infections. Induce rise in IgE and eosinophil levels.
What cytokines cause differentiation to Th17?
IL-6, IL-1beta
What cytokines are released by Th17 and what TF controls it?
Secretes IL-17
TF = RORgammaT
What type of infections are Th17 cells important for and what immune cells do they activate?
Protect against fungi by neutrophil recruitment and controlling barrier function
What is Tfh?
T follicular helper cells express Bcl-6 to influence B cell response through class switching from IgM. Also provides helper phenotypes to B cells.
What allows Tfh to migrate into B cell zone?
CXCR5
What is the function of Treg?
To regulate immune responses by restricting costimulatory availability of other T cells and secreting regulatory cytokines.
What TF is expressed in Treg?
FoxP3
What condition occurs if there is a defect in Treg cells?
AI
