T-Cell Biology Flashcards
CD4+ cell info
65% of T cells in blood
Can differentiate into Th1,2, or 17
middlemen of adaptive immune response
interact with MHC class II
CD8+ cell info
release cytolytic enzymes like granzyme and perforin to destroy cells via apoptosis
target virally infected cells and tumor cells and interact with MHC class 1
places of T lymphocyte maturation
bone marrow to thymus to blood/periphery
names of T lymphocyte stages of maturation
stem cell (marrow) (double negative b/c no cd4 or 8) pro-T (thymus) Pre-T (thymus) double positive (Cd4 and cd8) (thymus) Single positive (one of cd4/8) (thymus) naive mature T cell (periphery)
double negative thymocytes importance
no cd4 or 8 but up regulate the production of the membrane glycoproteins which is followed by TCR gene arrangement and then generation
positive selection in thymus
double positive thymocytes are tested to see if they will bind self MHC class I and II molecules…those that bind with low or moderate affinity are allowed to keep on developing
those that do not recognize the MHC I or II molecules or bind them too tightly will be destroyed
negative selection in thymic education
medulla thymic epithelial cells then ask the developing T lymphocytes if they recognize self antigens…those that bind any self peptide with high affinity will be destroyed
leads to tolerance of our own proteins…
1st signal in T cell binding
this is signal when the TCR successfully binds to the MHC molecule and the peptide presented
2nd signal in T cell binding
complete T cell activation…is the interaction of CD28 from the T cell and B7 from the antigen presenting cell surface
anergism
when T cell does not have second signal in pathway…no CD28 or B7 activation …the T cells are no longer responsive to antigen stimulation
“mechanism of self tolerance induction”
CD3 proteins
proteins with long cytoplasmic tails that are associated with the TCR complex
immunoreceptor tyrosine based activation motifs (ITAMs)
on ends of CD3 proteins in the TCR complex, phosphorylated once the TCR has bound
importance TCR/MHC complex and CD28 for IL-2
drive initiation (complex) and expression (CD28)
CD25
this is the IL-2 receptor and when IL-2 binds the CD25 it promotes cell division
CD40 ligand and receptor
ligand found on helper T cell (CD4) and the receptor on a macrophage…it enhances the activation of the macrophage
receptor can also be found on a B lymphocyte and will lead to antibody secretions
dendritic cells role in adaptive immune response
the dendritic cells are in charge of telling the CD4 helper cells what cytokines they are going to make…
if the CD4 cells are the quarterback then the dendritic cells are the coach
Th1 Cell cytokines
IFN-gamma, TNF-alpha
Th1 cell immune reactions
activate macrophages, increase IgG production, blocks Th2 cell development
Th1 cell host defenses
intracellular microbes, mainly bacterial
Th2 cell cytokines
IL-4,5,13
Th2 cell immune reactions
mast cell, eosinophil activation, IgE production, macrophage activation
Th2 cell host defenses
helminthic parasites
Th17 cell cytokines
IL-17, 22
Th17 immune reactions
neutrophilic, monocytic, and inflammation
Th 17 host defenses
extracellular bacteria and fungi
early source of IL-4 in the Th2 cell pathway
basophils
IL-4 roles in immune response for Th2
promotes B cell proliferation, IgE class switching, recruits eosinophils, blocks Th1 cell differentiation
IL-5 roles in immune response for Th2
elicits B cell growth, activates eosinophils and enhances IgE production
cytokines needed for Th17 growth
IL-6 and TGF-beta
Two ways CD4 cells help activate CD8 cells?
- can make cytokines that stimulate CD8 differentiation
2. can enhance the ability of APCs to stimulate CD8 differentiation
Do CD8 cells use the B7/CD28 signal?
yes, they also must experience the two signal step to be activated
CD8 cell or cytotoxic cell mechanism to apoptosis
antigen binding recognizes a target cell and binds to it…once bound granule exocytosis from CD8 cell…the perforin then helps granzyme enter into the target cell and granzyme induces apoptosis
high T cell levels autoimmune disease?
systemic lupus
low T cell level disease?
HIV/AIDS
T cell activation by bacterial shock…what happens?
massive T cell response…toxic shock syndrome, food poisoning etc.
cytokines needed for Th1 cell differentiation?
IL-12 and IFN-gamma
