Lecture 6: Adaptive Immunity 3- Part 3 Flashcards
Describe the process of how the antigen is uptaken into the cell?
1) The antigen is taken up by ENDOCYTOSIS into intracellular vesicles- by binding of antigen to various RECEPTORS found on APC- eg FC receptors
- Forms endosome
What happens to endosome once it is inside the cell and what happens to the ingested proteins?
-It FUSES with lysosome- makes the environment ACIDIC
-Acidification activates PROTEASES
which DIGEST the ingested proteins into peptides- Endolysosomes
What happens to digested peptides from the endolysosmes?
peptides fragments are loaded onto MHC II molecules
Describe the structure of MHC II?
MHC class II @ and Beta chains associate in the ER
What happens to the degraded peptides derived from the endocytic pathway?
Bind to the MHC class II molecules
Where do the MHC class II are sorted into vesicles?
Trans golgi network
What happens to these vesicles with MHC class II?
-Delivered to specialised compartments where peptide loading occurs
What blocks the binding of peptide on MHC class II in the ER?
Invariable chain
what happens to the invariable region inside the vesicle?
cleaved invariable region- leaving CLIP (class II associated invariant chain polypeptide) fragment inbound
What removes CLIP molecule from MHC class II?
HLA-DM (human leukocyte antigen DM- protein) facilitates the removal of CLIP
Where does the class II MHC loading take place?
ENDOSOMES- where acidic pH is required for protein degradation into peptides
What is CLIP molecule exchanged with?
foreign peptide- loaded onto MHC Class II
what do the CD4+Th cell activated by?
exogenous antigens
what needs to happen to the foreign antigens before they can be noticed by CD4+Th?
-Taken up by APC, degraded and presented
what is the result of the activation of the CD4+Th?
-Activation of macrophages- production of secreted antibodies by the plasma cells
