MHC Ag Flashcards
Importance of the Major Histocompatibility Complex
- CD4 and CD8 activation T cell activation
- B cell activation
- Disease susceptibility
- vaccine development strategies
Professional antigen presenting cells
macrophages and B cells
Exogenous Pathway
antigen comes from outside the cell.
- antigen is presented to CD4+ (helper) T cells
- This presentation required MHCII molecules
- Contributes to CD4+ responses (activation)
- expands CD4+ effector cells
Which cells express MHC II
dendritic cells, B cells, macrophages
Steps of Antigen Processing with MHC II
- antigen capture and uptake
- internalized antigen degraded
- generation of MHC II/peptide complexes
- transport of MHC II/peptide complexes to cell surface
Steps of Antigen Processing by B cells
- antigen capture and uptake by B cell receptor
- internalized antigen degraded by endocytosis- membrane pinched off, neutral pH, antigen is processed by catalytic enzymes
- MHC II are generated in endoplasmic reticulum. Peptides become associated with MHC II
- Peptides displayed on cell surface in the MHC II
What is required for efficient antigen capture by B cells?
high affinity antibody
Steps of Antigen processing by macrophages
- phagocytosis of microorganisms
- phagocytic vesicle fuses with an intracellular lysosome forming phagolysosome, pH >5
- MHC II are generated in endoplasmic reticulum. Peptides become associated with MHC II
- Peptides displayed on cell surface in the MHC II
Non-professional antigen presenting cells
epithelial, endothelial, stromal. Interferon gamma can induce MHC II
Goal of MHC II
activation of T helper cellsq
Endogenous Pathway
MHC I- peptide produced inside cell
MHC I Pathway
goal is to stimulate cytotoxic T cells to destroy altered or infected cells. MHC I molecules are present on almost all nucleated cells
Steps of MHC I Pathway
- endogenous antigen produced in cell
- antigen tagged by ubiquitin
- antigen enters proteasome
- antigen degraded into peptide fragments 8-10AA
- peptide released into cytosol
- migrate to ER via TAP-1 and TAP-2
- moves to ER
- MHC I binds peptide
- moves to golgi
- peptide antigen displayed on cell surface with MHC I
What does captured antigen become?
it is cleaved by proteases into peptides
Cell stimulated in MHC I
CD8 cytotoxic T cell