5. Antigen Capture and Presentation to Lymphocytes Flashcards
What kind of T Cells have a higher specificity for unconventional antigens like heat shock proteins and phospholipids?
gamma-delta T Cells
What specific task of the immune system would be impossible without T Helper Cells?
Creation of immunological memory
What structure is encoded for by MHC Class 1 genes?
The polymorphic heavy chain of MHC 1
What does it mean to be a “nonresponder” to an antigen?
A patient cannot bind any peptide for a given antigen.
What signaling compound increases the production of MHC I and II?
Interferon gamma (IFN-y)
What do we call the part of the antigen that interacts with the MHC?
Anchor residues
What are the primary specific functions of T Helper 1 cells?
Production of IFN-y to activate Macrophages and help develop cytotoxic T Cells
Deals with Intracellular Microbes
Where can a B Cell recognize antigens?
Soluble in plasma, or on the surface of a cell
What two regions will you find on a T Cell receptor domain?
Constant and variable regions
What all makes up the T Cell receptor complex?
TCR (constant and variable regions)
and
CD3
What cytokine stimulates clonal expansion of activated T Cells?
IL-2
What are the three main professional antigen presenting cells?
What MHC do they produce?
Macrophages
Dendritic cells
B Cells
MHC II
What kind of T Cell can recognize molecules that don’t appear to need any processing?
Gamma-Delta (yd) T Cells
What two structures make up 90% of T Cell Receptors?
Alpha and Beta polypeptide chains
Which MHC presents antigens from extracellular pathogens?
MHC II
What is the function of the CD4 and CD8 receptor?
To recognize the invariant part of the MHC the T Cell intends to interface with
What cytokine is important for B Cell proliferation?
IL-4
What two things are recognized when a TCR binds to an antigen presenting MHC?
The antigen residue itself, as well as the residues of the MHC molecule
Which MHC do CD4+ T Cells (T Helper Cells) respond to?
MHC II
What is significant about the genetics of MHC?
It uses codominant expression, where both the mother and the father’s alleles are expressed.
Which MHC complex is of concern when considering a match for organ transplant?
MHC I
In which region is the antigen binding site on a T Cell receptor?
In the variable region (just like Ig)
Where is an antigen captured in the blood stream likely to be presented?
In the spleen
What is the function of CD3?
Senses conformational change in the TCR and creates a signalling cascade within the T Cell to let it know it’s bound to something.
What are coded for by MHC (HLA) Class 2 genes?
Two dissimilar polymorphic polypeptides chains (alpha and beta), both of which contribute to the peptide binding groove
What is an immunodominant peptide of an antigen?
The peptide that can be presented by a given patient’s MHC for a given antigen.
What structure is joined with the polymorphic heavy chain in MCH 1?
An invariate Beta2-microglobulin that does not participate in the binding groove for peptides
What is the effect of antigen presentation in a macrophage, since they cannot activate naive T Cells?
They show the T Cells where the pathogens are. When macrophages no longer present the antigen, the T Cells undergo apoptosis (contraction of the immune response)
Also the effector T Cell encourages the macrophage to destroy the phagocytosed pathogen
What enzyme actually packages antigens onto MHC I molecules in the endoplasmic reticulum?
ERAP
(Endoplasmic Reticulum Associated Peptidase)
What are the six alleles for MHC Class II ?
Maternal and Paternal:
DR
DP
DQ
What is the function of CLIP?
CLass II associated Invariant chain Peptide
Prevents self peptides from binding to the variable region of MHC II as it’s in the endoplasmic reticulum before being packaged into vesicles for presentation on the cell surface
Which MHC do CD8+ T Cells (Cytotoxic T Cells) bind to?
MHC I
(MHC is produced on almost all cells, and cytotoxic T Cells would need to be able to kill any infected cell.)
What specific way must an antigen be presented to an Alpha-Beta T Cell?
It must be a peptide fragment of a protein antigen
It must be presented on an MHC molecule
It must be a linear antigen (small peptide)
What dendritic cell receptors drop in production after activation?
Mannose
Fc receptor
This alarm system is necessary before activation, but once an antigen is found, the dendritic cell focuses on antigen presentation and T Cell activation
What happens when an antigen presenting B Cell presents to an effector T Cell?
The B Cell is encouraged to become a plasma cell and begin producing antibodies
What are the primary functions of T Helper 2 cells?
Produce IL-4 which helps B Cells become plasma cells and produce antibodies, as well as helping them to become memory cells
Deals with extracellular pathogens
What are the three functions of HLA-DM?
Catalyzes the removal of the CLIP protein from MHC II
Stabalizes MHC II
Facilitates the binding of the antigen to MHC II’s open binding groove
What is the only cell that can activate a naive T Cell?
Dendritic cell
How are viral particles picked up by professional antigen presenting cells shown to CD8 T Cells?
The phagosome leaks some viral protein into the cytosol where it is broken down and presented on the professional antigen presenting cell’s MHC I, simulating itself being infected with a virus.
This is called cross presentation.
Which MHC has a glycosylated alpha chain?
MHC I
What chains make up CD3?
Gamma
Delta
Epsilon
Epsilon
Zeta
Zeta
(two zetas)
What transporter moves ubiquitinated viral proteins into the ER to be packaged on MHC I?
TAP
(Transporter associated with Antigen Processing)
Which MHC binds larger peptides?
MHC II (10-20 peptides)
