W2_04 T Cells Flashcards
which factors are important in a Th cell to turn a B cell into a plasma cell?
MHC complex (+CD4), CD40L, cytokines (IL-4,5,6)
which 2 signals do macrophages need to be activated and digest phagocytosed contents?
IFN-gamma (from Th1);
CD40L from T cell onto CD40
what are the two classes of TCRs? which is more common?
alpha:beta; (more common)
gamma;delta
what is part of the TCR complex?
the TCR itself (alpha:beta),
CD3 complex (gamma, delta, epsilon, zeta),
CD4/CD8 co-receptor
what are the gene components of the TCR recombination?
V and J
how do T cells travel through lymphoid organs as they develop?
precursor goes from BM to thymus to mature;
T cells go to secondary lymphoid tissues
what’s the difference in the specificity of the TCR and BCR?
BCR can bind to any exposed antigen.
TCR can only bind to specific segments of a protein, even those that are normally hidden by folding, so proteins need to be chopped up to be presented to T cells
HLA A, B, C is which type of MHC class?
MHC class I (mnemonic: has 1 letter)
HLA DP, DQ, DR is which type of MHC class?
MHC class II (mnemonic: has 2 letters)
where do you find MHC class I molecules?
on all cells
where do you find MHC class II molecules?
on APCs only
what are the components of MHC class I?
3 alphas + 1 beta
what are the components of MHC class II?
2 alphas + 2 beta
note: MHC is stable and DO NOT REARRANGE
diversity is inherited; we can have up to 6
CD8 cells match to which MHC?
MHC class I; CD8 on killer T cells
CD4 cells match to which MHC?
MHC class II; CD4 on Th cells
where does antigen bind to MHC I during preparation?
in the ER
where does antigen bind to MHC II during preparation?
in the phagolysosome
where are dendritic cells found in the thymus?
medulla
where are cortical epithelial cells found in the thymus?
cortex
how do T cells develop with their receptors?
beta, gamma, delta first.
then alpha, gamma, delta
how do T cells move through the thymus as they mature?
start in the medulla. meet dendritic cells. move to cortex. and mature to double-negative near the surface. head back towards cortico-medullary junction and become mature double-positive cells.
what is positive selection?
identifies T cells that can recognize self-MHC
what is negative selection?
identifies T cells that recognize self antigens
how do T cells have negative selection for tissues outside the thymus?
AutoImmune REgulator (AIRE) allows epithelial cells in the thymic medulla to secrete self Tissue Specific Antigens. so T cells that bind to these are negatively selected for.
what is required for co-stimulation of T cells?
B7 must exist on the APC. this binds to CD28 on the T cell.
what happens to the T cell w/o co-stimulation?
T cell becomes anergic
what are the transcription factors for TCR and CD28?
NFAT and AP1
which cytokine is responsible for T cell proliferation and differentiation?
IL-2. T cells have receptors AND produce it. causes burst of proliferation.
which 2 mechanisms can CD8 cells kill?
lytic granules;
FasL-Fas interaction
Th1 induced by?
IFN-gamma; IL-12
Tfh induced by?
IL-6, IL-21
Th2 induced by?
IL-4
Th17 induced by?
IL-6, TGF-beta
Treg induced by?
TGH-beta
which two stimuli do macrophages need to be activated?
IFN-gamma;
CD40L
what do Th1 cells do?
macrophage activation to fight intravesicular pathogens (e.g. bacteria + viruses)
what do Th2 cells do?
B cell antibody production (IgA + IgE) for parasite and extracellular bacterial fighting
why do granulomas form?
when the macrophage can’t digest the material. there are giant cells, a bunch of macrophages, and a rim of T cells
what are the cytotoxins of the T cell?
perforin and granulysin make pores in the target cell membrane,
granzymes are the lytic granules
what is leprosy?
an infection with mycobacterium leprae. bacteria infect the macrophages and aren’t easily digested. thus, T cells polarized to Th1 response.
how does tuberculid leprosy manifest?
slow damage to skin and peripheral nerves
what is lepromatous leprosy?
bacteria grow unchecked outside the cells. T cells polarized to Th2. severe tissue destruction
name some mechanisms of tolerance
negative selection in BM;
anergy induction in autoreactive T and B cells;
suppression of autoimmune responses by regulatory T cells;
expression of tissue specific proteins in the thymus
name 2 mechanisms of peripheral tolerance
anergy if they don’t receive co-stimulation;
suppression by regulatory T cells
which important transcription factor is associated with Treg cells?
Foxp3
what are the two subsets of Treg cells?
natural (nTreg) from thymus;
inducible (iTreg) from peripheral naive T cells
