Antigen Presentation Flashcards
How were Major Histocompatibility Complexes discovered
Due to their importance during tissue rejection
Major Histocompatibility Complex is encoded where
Human Leukocyte Antigen Complex on Chromosome 6
What are Major Histocompatibility Complex genes
Polygenic, extremely polymorphic, Codominantly expressed
Major Histocompatibility Complex molecules are neccessary to
Present Ag to T cells
Who has MHC Class I
All nucleated cells
What do MHC Class I display
Endogenous peptides
What do MHC Class I present to
CD8+ T cells
Who expresses MHC Class II
on professional antigen presenting cells
What do MHC Class II present
exogenous peptides
Who do MHC CLass II present to
CD4+ T cells
Strucutural difference between Class I and Class II MHC structures
Class I, only in membrane once, where class II enters cell membrane twice
MHC Peptide Binding region for Class I and Class II
Class I: 8-10 amino acids
Class II: 13-18 amino acids
The breakdown of macromolecules into amller fragments in order to prepare for presentation to a t cell
Antigen Processing
4 ways of Ag Processing
Exogenous, Endogenous, Cross-presentation, autophagic
endogenous pathway
Infection by bacteria, antigen degraded in ctosol, peptide association with MHC Class I, activation of CD8 Tc Cells
Exogenous Pathway
Internalization by APCs, antigen degradation in endocytic compartment, peptide assocation with MHC class II, Activation of CD4 Th cells
Cross presentation
Starts in exogenous pathway and ends in endogenous pathway (outside but MHC class I)
Autophagic
Starts in endogenous pathway and ends in exogenous pathway (inside but MHC class II)
Naive T Cell Activation
Uses a Dendritic cell to take up antigen, and results in Clonal expansion and differentiation into effector T cells
Effector T cell activation
Marcrophase presnts, leading to T cell activation and activation of macrophages for Cell-mediated Immunity
And B cell activation and antibody production leading to humoral immunity
What i contained in the Alpha subunit of MHC Class I
Enter into the membrane and have the peptide binding chain
Subunits of MHC CLass I
Alpha and Beta subunits both insert into the membrane and also have a peptide binding cleft
3 types of Antigen Presenting Cells
Mature DC, Macrophages, B cells
What is the best at presenting to a T cell
Dendritic cells (high MHC II and constimulary molecules)
What can activate a Naive T cell
Dendritic cells
What are macrophages and B cells good activating
Effector cells and memory T cells
Action of Dendritic Cells
Recognize antigen, Phagocytosis it, activating DC cell. Begins processing, drain through lymphatics , to find the correct T cell, to activate that T cell
Exogenous Pathway
Internatlize antigen by phagocytosis to form phagosome. This fuses with lysosome to bread down antigen. At the same time the RER begins making Class II MHC. Passes throught the SER, Golgi, then heads to Lysosome, to degrade invariant chain. HLA-DM removed clip and peptide from antigen to be presented on the outside of the cell.
What parts are uniquie to the exogenous pathway
Invariant chain, Clip, HLA-DM, MHC II
Endogenous Pathway
Internal peptide has a tag added to it from the Ubiquitin Protein. Tis tells the protein to be degraded by the proteosome. TAP puts these fragments into the endoplasmic reticulum and is loaded into MHC Class I
Cross Presentation pathway
APC ingest and processes virally infected cell. Viral Proteins enter the cytosol and is processes via endogenous pathway(protesome) to activate a CD8 cell via MHC I