T Cell Activation and Generation of Effector T Cells Flashcards
MHC class 1 presents {?} antigen but MHC class 2 presents {?} antigen
MHC class 1 presents endogenous antigen but MHC class 2 presents exogenous antigen
Upon leaving the Thymus what do Naiive T celle enter lymph nodes via?
Naiive T cells upon leaving the thymus enter lymph nodes via a high endothelial venule which is a specialised blood vessel
T cells use {?} lymphatic vessels to move between lymph nodes
T cells use efferent lymphatic vessels to move between lymph nodes
Dendritic cells presenting an antigen can move from a site of infection through an {?} to the lymph node to present to naiive T cells
Dendritic cells presenting an antigen can move from a site of infection through an afferent lymphatic vessel to the lymph node to present to naiive T cells
Activated T cells move into the circulation through the {?}. And move to sites of infection due to {?} instead of circulating.
Activated T cells move into the circulation through the thoracic duct (vena cava). And move to sites of infection due to chemokines instead of circulating.
Explain why a T cell would recirculate and what this means?
If a naiive T cell does not encounter its specific antigen (being presented by a dendritic cell) in either of the lymph nodes it travels through (only 2 LNs?). Then it will recirculate and go back into the first lymph node again.
Naiive T cells are activated in {?} lymphoid organs such as {?}
Naiive T cells are activated in secondary lymphoid organs such as lymph nodes and spleen
How do naiive T cells encounter their antigen in a LN when the antigen would likely be at the site of infection (where the pathogen is)?
As dendritic cells presenting the antigen move into LNs by afferent lymphatic vessels
Explain how there are 2 stages of activation from a naiive T cell
- There is activation of the naiive T cell to an effector cell
- And there is activation of the effector T cell (can happen in periphery at sites of infection) which is functional differentiation of the cell
Name 3 cells that can activate naiive T cells
- Dendritic cells
- Macrophages
- B lymphocytes (can pick up soluble antigen with their BCR on surface and present to T cells)
Only activated professional APCs such as the ones above present high levels of MHC class 2
Professional APCs express {?} and high levels of {?} when activated
Professional APCs express co-stimulatory molecules and high levels of MHC2 when activated
Name the 3 signals needed for a T cell to be fully activated and differentiated into an effector or memory T cell
- Signal 1: Antigen recognition
- Signal 2: Co-stimulation
- Signal 3: Cytokines - Part 3
Which of the 3 professional APCs is the costimulatory signal mostly found on
Dendritic cells
- but also found on macrophages and B cells
The co-stimulatory signal for a T cell involves the binding of {?} from a T cell to {?} on the APCs
The co-stimulatory signal for a T cell involves the binding of CD28 from a T cell to B7 on the APCs
- B7 is a common term for B7-1 (CD80) and B7-2 (CD86)
Dendritic cells that have been activated in the presence of PAMPs upregulate {?} and {?}
Dendritic cells that have been activated in the presence of PAMPs upregulate B7-1 (CD80) and B7-2 (CD86)
Name 2 important cyctokines in the activation of T naiive T cells by an APC
IL12 released by the APC
IL-2 released by the T cell (paracrine)
- also IL-6 IL-4 and TGf-beta
T cells recognise antigen with or without costimulators, causing the expression of {?} on T cells
T cells recognise antigen with or without costimulators, causing the expression of CD40L on T cells
Describe HOW detection of PAMPs can help to induce T cell activation (this is the mechanism of the danger hypothesis)
- this is also how a cd4+ cell choses between TH1 and TH2
- Dendritic cells with their MHC bound to a TCR and CD80/86 bound to CD28 (and also other co-signals such as CD40L) may detect some PAMPS by their PRRs.
- These PRRs will cause signalling which can allow for cytokine release to affect the T cell and drive it to activate.
- These cytokines can push the cell become either TH1 or TH2.
- So PRR binding stimulates:
- B7 (CD80/CD86) increase
- Polarising cytokine release
So what is an important function of this 3rd signal of cytokines on T cells?
Induction of T cell polarisation - so cytokine environment (from the APC) causes the cell to decide what it will differentiate into, do not know if this is for CD8+ cells also but CD4+ is below
When cytokines bind to T cells, what happens to induce their polarisation?
- is signal 3
In response to certain cytokines, each effector T cell will express a master controller transcription factor which controls the expression of the cytokines expressed by that T cell
Describe the functions of the below surface receptors - these are expressed one after the other over time
- CD69 (on tissue resident cells) allows for retention in the lymph node so they can be fully activated
- CD25 is receptor for IL-2
- CD40L is needed for further activation by denderitic cells
- CTLA-4 is expressed days after to calm/regulate the response
Upon activation, what does a T cell do and what choice does it need to make
- Proliferation by IL-2
- Differentiation
- Choice to become effector or memory cell
TH1 polarisation occurs in response to the presentation of {?} by an APC
TH1 polarisation occurs in response to the presentation of intracellular pathogens such as viruses and bacteria by an APC
- Remember that TH1 cells are for removing intracellular pathogens
The main polarising cytokine in TH2 cells (IL4) causes activation of the transcription factors {?} and {?}. {?} promotes activation of IL4 and IL13 genes.
The main polarising cytokine in TH2 cells (IL4) causes activation of the transcription factors STAT6 and GATA3. GATA3 promotes activation of IL4 and IL13 genes.
- So the IL4 is an autocrine response
Describe the functions of TH2 cells fully
- Which cytokines do they secrete?
- Which class switching do they initiate?
