LW - antigen presentation and cytokines Flashcards
What are the roles of T-cells in the adaptive immune response?
- Control/eliminate infection.
- Important for immunity and response to a vaccine.
- Kills cancerous cells.
- Role in disease pathogenicity.
- Therapeutic applications.
What is antigen processing?
Generation of small peptide fragments which are bound to MHC and transported to the cell surface.
What is the purpose of antigen processing and presentation?
- T-cells cannot recognise complex or whole antigens.
- Must be converted first to be bound to MHC.
- Achieved by; antigen uptake, antigen processing and antigen presentation at the cell surface.
What can T-cells recognise?
- Small peptide fragments bound to MHC molecules.
- This is expressed at the cell surface.
- TCR are responsible for recognising cell surface peptides.
What is the processing pathway for endogenous antigens?
Processed and presented with MHC class 1 molecules. Peptide fragments: 8-14 AA. ER conjugates antigens and MHC class 1 molecules. TAP (transporter associated with antigen processing) delivers peptides to the ER. Proteosome generates peptide fragments from cytosolic protein. In an immune response this is induced by interferon, modifications in the proteasome mean that it produces peptides that bind well to MHC1.
What is the processing pathway for exogenous antigens?
Processed and presented by MHC class II molecules. Presented peptide fragments: 15-24 AA. Taken up tiny intracellular vesicles. Acidification of vesicles activates proteases to degrade the antigen into protein fragments. Fragments fuse with the MHC class II molecules.
What is the function of a conventional dendritic cell?
Activates naive T-cells.
Highly potent APCs.
Phagocytosis of antigens.
Macropinocytosis of surrounding fluid non-specifically.
Uses PRR to recognise pathogens and respond by secreting cytokines.
What is the structure of a conventional dendritic cell?
Structure - multiple membrane outgrowths called dendrites. Large surface area to increase efficiency of antigen uptake.
How do dendritic cells mature?
- Dendritic cells take up microbial antigens and become activated in peripheral tissues.
- Activated dendritic cells travel to the lymph nodes.
- In the lymph node, dendritic cells become mature and activates T-cells.
What are the 3 main properties of a mature dendritic cell? Why are these properties important?
- Increase number of MHC molecules.
- Express co-stimulatory molecules - CD80 and CD86.
- Secretes cytokines.
- This is important because it provides dendritic cells with a potent ability to activate naive T-cells.
What are Langerhan cells?
Immature conventional dendritic cells. Actively phagocytic. Birbeck granules - large. Reside in the skin. Pick up antigen in the skin and migrates to regional lymph nodes.
What are plasmacytoid dendritic cells?
Generates a large amount of anti-viral interferons.
In response to a viral infection.
Not as important in activating naive T-cells.
What cells express pattern recognition receptors?
Dendritic cells.
Why are Pattern Recognition Receptors important?
Recognise highly conserved microbial components. These are not easily altered by microbes to avoid detection.
PAMPs - pathogen-associated molecular patterns.
DAMPs - damage-associated molecular patterns.
Sugar, protein, lipid and nucleic acid motifs.
Why are Pattern Recognition Receptors important?
Recognise highly conserved microbial components. These are not easily altered by microbes to avoid detection.
PAMPs - pathogen-associated molecular patterns.
DAMPs - damage-associated molecular patterns.
Sugar, protein, lipid and nucleic acid motifs.
