Dendritic cells and antigen presentation Flashcards
immature dendritic cells are
good at phagocytosis but bad at presenting antigens
MHC I in the
cytosol
MHC II in the
endosomal compartment
MHC I on
all cells
MHC II on
APC, B cells and macrophages
activation of immature dendritic cell
1) PRR e.g. TLR4 recognise LPS
2) DC matures and prepares to become an APC
3) peptide anti from invading bacteria, regionally extracellular, are endocytosided
4) combine with MHC II
5) then this complex is presented on the cell surface
6) also increase in costimualtory molceules
costimulatory moleucles
CD80/86 increase
immature DCs are located i the
tissues throughout the body, including skin, git, respiratory tract
encounter with a pathogen induces
the DC to matute
T cells express which co receptors
CD8 -MHC I
CD4- MHC II
what stimulates Th17
IL-6
what does Th17 produces
IL-17 and IL-6 –> neutrophil recruitment
MHC II –>
CD4 T cell- T helper cell
MHC I –>
CD8 T cell- cytotoxic T cell
each T cell only has one
TCR which specific to pathogen
DC presentation to CD4 T cell
1) T cell receptor binds to MHC II peptide molecule
2) CD4 receptor on T cell binds to MHC II complex
3) CD28 (T cell) binds to CD 80/86 costimulatory molecules
cytokine help Th cells decide
which subclass to differentiation into
what stimulates Th1
IL-12
what stimulates Th2
IL-4
Th1 release
IFN-Y AND TF-A
- macrophages
- cytotoxic T cells
Th2 release
IL-4, IL-5 and IL-13
- B cell activation
- allergic respomse
B cells reconginise
intact antgins
T cells recognise
fragments of protein antigen - degraded inside APC
antibodies can act
far away- humoral
T cells ave a
short range effect
cytotoxic T cells
directly kill virally infected cells and other cells infected with intracellular pathogens
T helper cell
helps stimualtemacrophages, B cells and cytotoxic t cells
CD8 and CD4 cells must be
activated to proliferate and differentiate into effector cells
main types of APC
macrophages DC and B cell
cytotoxic T cells protect against
intracellular pathogens- sheltered from antibodies
CD8 T cell activation
- once activated by APC (MHC I), CD8 T cells become effector T cells- will kill any target cell infected with same pathogen
- once bound to the target cell, CD8 T cell will release a pore-forming protein called perforin
- this mediates entry of granzymes into target cell
- mediated apoptosos
apoptosis by Cytotoxic T cell
Target cell which presents antigen on MHC I
- perforin binds and facilities entry of grnazymes into cell via pores
- granzymes cleave BID, causing cytochrome C to release from mitochondria into cytosol
- cytochrome C activates pro-caspase 3
- pro-caspase 3 cleave ICAD- inhibitor of CAD
- CAD degrades DNA ensuring cell death
