Antigen Presentation Flashcards
What cells are classified as professional antigen presenting cells?
Macrophages, Dendritic cells, and B cells
Dendritic cells present both _________ and ________ antigens, following processing, in MHC molecules to _______ CD4+ and CD8+ T lymphocytes.
Extracellular
Intracellular
Naive
_________ and _ ______ present only ________ antigens to T _______ cells.
Macrophages and B cells
T helper cells
When are macrophages presenting processed extracellular antigens to CD4+ T lymphocytes?
During the effector phase of cell mediated immunity, a from of the adaptive immune response where no antibodies are needed
When are B cells presenting processed extracellular antigens to CD4+ T lymphocytes?
During the humoral response of the adaptive immune reponse, where antibodies are being genereated from differentiated B cells
Mature recirculating T cells that have not yet encountered their antigens are known as -?
Naive T cells
A naive T cell must first encounter an antigen, and then be induced to proliferate and differentiate into _______ T cells capable of contributing to the removal of the antigen, as they act _______ to remove that ________ antigen.
Effector
Quickly, rapidly, etc.
Specific
True or False: Dendritic cells will present antigens to effector T cells in the thymus for activation.
False, they present only to naive T cells
What form of dendritic cell has a lymphoid precursor?
Plasmacytoid DC
What precursor is associated with Langerhans cells, which are a form of dendritic cell?
Myeloid
Where will macrophages be found in the body?
Lymphoid tissue, CT, and body cavities
Where will dendritic cells be found in the body?
Lymphoid tissue, CT, and epithelium (langerhans cells)
Where will B cells be found in the body?
Lymphoid tissue and in circulation
Which form of antigen presenting cell has the lowest concentration of MHC II molecules expressed?
Macrophages
What two important functions are associated with APC’s?
- Co-stimulation
- Antigen processing and presentation
MHC II moleculse are associated with presenting ____________ antigens to CD_+ T lymphocytes.
Extracellular
CD4+
Which antigen presenting cells will produce MHC II molecules to T lymphocytes?
Macrophages and B cells to Effector T cells, and Dendritic cells to Naive T cells
Which antigen presenting cells will synthesize MHC I molecules to T lymphocytes?
Dendritic cells to Naive T lymphocytes
MHC I molecules are associated with _________ antigens being expressed for CD_+ T lymphocytes.
Intracellular
CD8+
In the phago-endosome the processed peptides are loaded on to the MHC-class ____ molecules, and then presented on to their surface. T ________ cells recognize these peptides along with MHC- Class ___ on the surface of antigen presentating cells for the initiation of immune response.
MHC class II
T helper cells
MHC Class II
APC’s can phagocytose exogenous antigen and process this antigen in the ________ and finally phagosome containing processed peptides fused with the ________ containing MHC Class ___ molecules
Phagosome
Endosome
MHC Class II
_________ T cells recognize antigen in the context of MHC class I antigen on the surface of viral infected cells or transformed cells in the body.
Cytotoxic T cells
Where are MHC molecules produced, prior to their association with antigenic peptides for antigen presentation?
rER or Granular ER
How are antigenic peptides collected and directed into the rER for association with MHC Class I molecules?
TAP1 and TAP2 protein transporters (transporter associated with antigen presenting proteins)
Uptake of extracellular antigens requires specific ________, and once they bind they are internalized into __________.
Receptors
Endosomes/ Phagosomes
What is present within endosomes as they attempt to digest the atigen?
Proteolytic enzymes
Through the process of phagocytosis, what does the endosome fuse to for further degradation of extracellular materials?
A lysosome to form a phagosome
What enzymes are present within the lysosomes that can degrade extracellular antigens into 14 - 20 aa length peptides for MHC II binding?
Cathepsins, which are lysosomal proteases aka proteolytic enzymes
The alpha and beta chains of MHC II molecules are formed in the -?
rER or Granular ER
Following synthesis, where will formed MHC II molecules be transported to through vesicles?
To the Golgi body, who send it to the endosome
What is present in the newly formed MHC II molecule prior to its association to 14 - 20 aa length, antigenic peptides? What happens to it?
An invariant chain, which will be degraded, leaving a small portion called the CLIP. This will be removed in the phagolysosome by HLA-DM for antigenic peptides to bind to the MHC II molecule
What is the destination for antigenic peptides produced in the cytosol?
They will be degraded by proteasomes, and the antigenic peptides produced will be transported into the rER via TAP1 and TAP2 proteins for association with MCH I molecules for presentation
What ogranelle is responsible for receiving MHC I: antigen complexes, and MHC II molecules (prior to antigen association)?
The Golgi complex
T helper cells once activated can -?
Release cytokines for B cell differentiation into plasma cells, or for increased macrophage phagocytic abilities
True or False: TCR’ are part of the immunoglobulin superfamly.
True
What two classes of TCR’s are there, and are they both MHC dependent or independent?
Alpha-beta = MHC dependent
Gamma-delta = MHC independent
TCR are associated with a CD3 complex that is associated with what units?
A single gamma unit and delta unit, two epsilon untis, and two zeta units
True or False: All the units associated with the CD3 complex are considered invariant as they do not contribute to the specificity of the TCR at all.
True
Which of the following is not true of TCR’s?
A) CD3 complexes are required for expression of TCR;s on T cell plasma membranes, it also signals intracellular pathways
B) TCR’s only recognize small and specific peptide sequences
C) TCR’s only recognize foreign peptides bound to appropriate MHC molecules, being restricted otherwise
D) None of the above
D) None of the above
B cells recognize _______ antigens on the antigenic surface, such as peptides, protein, NA’s, polysaccharides and lipids, and never ____ molecules.
Soluble
MHC
CD1 molecules, which are found only on APC’s and some _________ cells, are associated with the presentation of _____ antigens non-restricted ____ molecules.
Epithelial
Lipid
MHC
Co-stimulatory signals are required for full T cell activation. There are two signals, 1 and 2. How are they generated?
Signal 1 = from the binding ot the TCR:CD3 complex and MHC of the APC
Signal 2 = binding between CD28 of T cells with CD80/CD86 of the APC
What happens when there is no co-stimulatory signal present upon recognition of the MHC and TCR/CD3 complex?
Clonal anergy, which is the lack of responsiveness to an antigen despite the presence of antigen-specific lymphocytes
What does the following definition apply to:
The incomplete T cell activation, which is mostly observed in previously activated T cells. It is maintained by a block in the Ras/MAP kinase pathway, which can be reversed by IL-2 or anti-OX40 signaling, and usually does not result in the inhibition of effector functions.
Clonal anergy
What roles do TLR’s have on APC’s?
- Induce expression of MHC molecules and co=stimulators
- Increase efficienty of antigen presentation
- Activates APC’s, which produce cytokines for T cells
- Produce chemokines for chemotaxis
Naive T cells are activated in secondary lymphoid tissues and organs by ________ _____, which leaving the epithelium or CT and travel along _________ vessels to the nearest ______ _____.
Dendritic cells
Lymphatic
Lymph nodes
What qualities are associated with dendritic cells being the most effective antigen presenting cell?
- Strategic location at entry points
- Ability to capture and express intra- and extracellular antigens
- Migration routes to T cell rich areas in lymph nodes
- High expression of co-stimulatory molecules for full T cell activation
The presentation of antigens through both the Class I and II pathways in known as -?
Cross Presentation or Cross Printing
