Antigen Recognition by T cells Flashcards
How do B and T cells recognise Antigens?
What is the only APC able to present to NAIVE T cells?
→ What else do they do to activate the T cell? Why is this needed?
How do Macrophages activate CD4+ T cells?
How do B cells activate CD4+ T cells?
- B cells recognise antigens directly, while T cells only recognise the antigens presented by APCs
- Dendritic cells
→ Co-stimulation and Cytokines - Only antigen recognition isn’t enough to activate the T cell - They phagocytose microbes and present its antigens to CD4+ cells (Th1), which goes on to activate that macrophage to kill the ingested microbe
- They internalise the antigens, process it into peptides to present to CD4+ cells (Th2), which then goes on to activate B cells for antibody production
T Cell Receptor (TCR):
What do they bind to?
What is its structure?
→ Which part forms the antigen-binding site?
——————-
MHC:
What is MHC I presented to? On which cells is it found on?
What is MHC II presented to? On which cells is it found on?
What do both MHC’s have at the top of their structure?
- Peptide-MHC Complex
- 2 chains - α and β chains with a variable domain in each
→ Vα + Vβ
——————- - CD8+ cells and is found on all Nucleated cells
- CD4+ cells and is found on APCs
- Peptide-binding cleft
Antigen Presentation to CD4+ cells:
What type of antigens are used here?
What occurs with these antigens?
Antigen Presentation to CD8+ cells:
What type of antigens are used here?
What occurs with these antigens?
What then occurs for these antigens to be presented?
- Extracellular foreign antigens (Bacteria)
- Taken in and broken down into peptides by Endolysosome
- MHC II goes to Golgi apparatus to package into a vesicle, which fuses with the Endolysosome and the peptides bind to the MHC II
- Intracellular foreign antigens (Virus)
- Broken down into peptides by Proteasomes
- Peptides go into ER to bind to the MHC I, which then go to the Golgi apparatus to be put into a vesicle
