Antigen Processing and MHC (10)

Where does MHC class 2 antigen originate?

Extracellular

Where does MHC class 1 antigen originate?

Intracellular

Steps of MHC class 2 processing

Peptide production in phagolysosome, peptide binding by MHC class 2, and MHC class 2 presents peptide at cell surface

Steps of MHC class 1 processing

Antigen processing to peptides in proteasome, peptide transport into rough endoplasmic reticulum, peptide binding by MHC class 1, and MHC class 1 presents peptide at cell surface

Where are peptides produced in the cytosol transported to?

Into the rough endoplasmic reticulum

What does TAP stand for?

Transporter associated with Antigen Processing

Stabilizes MHC 2, prevents binding of peptides in RER, and directs MHC 2 to endosomes

Invariant chain

Steps of peptide loading onto MHC II

1. Invariant chain blocks binding of peptides to MHC class II molecules in the ER

2. In vesicles invariant chain is cleaved, leaving the CLIP fragment bound

3. CLIP blocks binding of peptides to MHC class II in vesicles

4. HLA-DM facilitates release of CLIP, allowing peptides to bind

What does CLIP stand for?

class II-associated invariant chain peptide

What is the only thing that can activate T cells?

Interaction between the antigen receptor and peptide antigen in an MHC molecule

Without [blank] there can be no effective immune response

T cells

what is the challenge placed on pathogens?

To evade the immune system and not get recognized by T cells

What two strategies were developed by MHC to maximize the T cell response to pathogens?

Multiple genes and polymorphism

More than one type of MHC molecule in each individual

Multiple genes

Extensive differences in MHC molecules between individuals

Polymorphism

What do multiple genes and polymorphism increase?

Diversity of MHC

What restricts T-cell recognition of antigens?

MHC

When will a given T-cell receptor recognize its peptide antigen?

Only when the peptide is bound to a particular form of MHC molecule

What is a biological consequence of MHC polymorphism and MHC restriction?

Transplant rejection

What is a biological consequence of MHC polymorphism that can also be considered an advantage?

Protection of the population from infectious diseases, but some individuals are more susceptible than others to infections

Each healthy animal is?

Able to produce diverse TCRs and BCRs but only contains limited number of MHC alleles

What can only containing a limited number of MHC alleles influence?

The T cell response to particular antigens, which in turn can affect antibody responses to those antigens

In a genetically diverse population, polymorphism in MHC alleles does what?

1. Enhances the population's ability to generate T cell and antibody responses to various antigens

2. Helps the population to develop protective immunity against various pathogens