Adaptive Immunity - T cells (part 2) Flashcards
What are the 3 signals required between dendritic cells and T cells for T cell activation?
TCR with MHC+antigen, costimulation, cytokines
What adhesion molecules (receptors) are present on dendritic cells?
ICAM-1, DCSIGN, CD58
What adhesion molecules (ligands) are present on T cells?
LFA-1, ICAM-3, CD2
How does binding between dendritic cells and T cells go from low affinity to high affinity?
T cells recognise MHC cells with an antigen, leads to conformational change in LFA-1 which leads to high affinity binding
What molecules are present on the dendritic cell for costimulation?
CD80/86
What molecules are present on the T cell for costimulation?
CD28
How are different types of CD4 cells generated?
cytokines form dendritic cells induces differentiation
What type of CD4 cells does IL-12 give?
Th1
What type of CD4 cells does IL-4 give?
Th2
What type of CD4 cells does IL-6/IL-21, IL-23, TGFbeta give?
Th17
What type of CD4 cells does IL-6 give?
TFH
What type of CD4 cells does TGFbeta give?
Treg
How do CD4 cells provide different functions?
By giving off different cytokines
What type of cytokines does Th1 release?
IL-2, interferon gamma, LT
What type of cytokines does Th2 release?
IL-4, IL-5, IL-13
What types of cytokines does Th17 release?
IL-17A, IL17F, IL-6, IL-21, IL-22
What types of cytokines does TFH release?
IL-21
What types of cytokines does Treg release?
TGFbeta, IL-10
What is the transcription factor involved in Th1?
T-bet
What is the transcription factor involved in Th2?
GATA-3
What is the transcription factor involved in Th17?
RORgammaT
What is the transcription factor involved in TFH?
Bcl-6
What is the transcription factor involved in Treg?
FoxP3
What is the function of Th1?
macrophage activation, isotype switching to IgG
What is the function of Th2?
mast cell activation, eosinophil activation, isotype switching to IgE
What is the function of Th17
neutrophil recruitment
What is the function of TFH?
Help B cell proliferation and differentiation
What is the function of Treg?
dampen down immune response once infection is clear
What is the difference between T-depedent and T-independent B cell responses?
T-depedent responses have protein based antigens and involves isotype switching, higher affinity antibodies and memory. T -independent responses are non-protein based antigens and doesn’t give isotype switching (only IgM), low affinity antibodies and no memory
How do CD4 T cells help B cells?
CD4 T cells express CD40L and B cells express CD40 - leads to isotype switching
Where do CD4 T cells and B cells meet?
At germinal centres at follicle/paracortex junction
How do B and T cells get to the germinal centres?
B cells down regulate CXCR5 and up regulate CCR7, T cells down regulate CCR7 and up regulate CXCR5 - and both follow chemotactic gradient
What kinds of cells are present at germinal centres?
Activate B cells, T follicular helper cells and follicular dendritic cells
What is the function of follicular dendritic cells?
Antigen depot that drives B cell activation and affinity maturation
How do CD4 T cells help in the activation of CD8 T cells?
CD4 T cells interact with dendritic cells to allow the dendritic cells to activate CD8 T cells - this is a function of the CD40L
What are the two ways which cytotoxic CD8 T cells kill infected cells?
Perforin punches holes in membrane to allow granzymes to enter and induce apoptosis or fas-ligand fas interactions lead to apoptosis
How do T cells get to the site of infection?
Because of expression of receptors - endothelial cells at site of infection express CCL5 and CXCL10 and T cells express CCR5, CXCR3 and VLA-4
