pre-IC2 MHC Flashcards
What are MHC proteins?
Cell surface proteins required for adaptive immune system to fn
Main immune fn of MHC molecules
Bind to peptide fragments (antigenic fragments), forming MHC-peptide complex, for recognition by T cell → aids the immune system to distinguish btw self and non-self antigen
Another name for MHC
Human leukocyte antigen
On which chromosome is the MHC gene found?
Chromosome 6
Examples of APC
Macrophages and dendritic cells
How is peptide-MHC complex formed, and what is it presented to?
Invading pathogen is recognised by APC,and gets engulfed by phagocytosis. During phagocytosis, bacterial proteins get broken up into peptide fragments called antigenic fragments → Each MHC class II protein binds to an antigenic fragment → peptide-MHC complex is presented to helper T cells
How many classes of MHC proteins are there? Which ones are involved in antigen presentation?
3 MHC protein classes; MHC Class I & II
Diff btw MHC Class I vs Class II (location, binding & antigen presentation)
MHC Class I
Present in nucleated cells & platelets. Not found in RBCs.
Binds to peptide fragment of endogenous antigens
Presents to cytotoxic T cells
MHC Class II
Present in APCs (macrophages, dendritic cells)andBcells
Binds to peptide fragment of exogenous antigens
Presents to helper T cells
What is a proteasome?
A protein complex ubiquitously present in cells to degrade unwanted/damaged proteins by proteolysis → proteins degraded to peptide fragments of ~15 aa
Example of endogenous & exogenous antigens
Types of endogenous antigens:
Normal self-antigen
Neoantigens found exclusively on cancer cells
Viral components from a virus-infected cell
Types of exogenous antigens:
Usually foreign antigens belonging to invading pathogens e.g. bacterial cells
How is the level of MHC expression regulated?
By cytokines e.g. IFN alpha & gamma
IFN alpha produced as an early response to viral infection → Increases transcription → Increases expression of MHC to activate appropriate T cells
IFN gamma is an immunomodulatory cytokine → Increases expression of MHC to activate appropriate T cells
How does the level of MHC expression affect the extent of T cell activation?
Incr in MHC expression, Incr in T cell activation
What are the key characteristics of MHC class I & II proteins?
Polygenic: Different MHC class I & II genes expressing different peptide binding specificities → provide broad coverage against antigens
Polymorphic: Each MHC gene has different alleles → different peptide binding specificities → provide broad coverage against antigens
