Adaptive immunity - T cells Flashcards
What does the cell mediated response involve?
-Extracellular vs intracellular
Where do cells, cytokines and pathogen antigens wash into?
-Lymphatic system
Label structure of Lymph node.
Label the structure of the spleen.
What does the white pulp contain?
What does it do?
The white pulp contains:
B cell corona -
Germinal centre – Antibody responses
Marginal zone – rich in macrophages and some B Cells
Periarteriolar sheath – mainly T cells
> Responds to antigens in the blood/ removes scenecent erythrocytes
To get help dendritic cells need to express co-stimmulatory molecules and necessary chemokines to reach lymphocytes. What up regulates this?
-TLR which recognise the antigen > expresses co stimulatory molecule
-intracellular infections : IFNα and IFNβ
What are the 2 types of T cells?
Describe the recirculation of T-cells in lymph nodes.
- T cells enter the lymph node via High endothelial venules into the paracortical area. (These venules have specialised endothelial cells which are cuboidal and express high levels of leukocyte receptors.)
- In the paracortical area T Cells interact with dendritic cells presenting antigen
- If they don’t encounter the antigen they recognise they continue out of the efferent lymph back into circulation
How do dendrites activate naive T-helper cells?
-Activation
-Survival
-Differentiation
- The T cell receptor recognises the antigen being presented and CD4 binds to the side of MHCII molecule - activation
- Co stimulation occurs B7.1/2 bind and signal to CD28, this induces CD40L on the T cell which signals back to CD40 - survival
- CD40L > CD40 instructs Polarising Cytokine release from antigen presenting cell then instructs the T cell what kind of T cell to differentiate into ( induce a variety of responses depending on which polarising cytokines they have been exposed to)
- The T cell produces IL-2 to act on itself and proliferate activated T-cell – autocrine signalling
What are polarising cytokines dependent on?
-The site and type of infection
What does it mean for a T-helper cell to be anergic?
- A T-cell is only activated if there are co-stimmulatory molecules displayed as well as antigen.. without this they come anergic e.g. self molecules
What is the polarising cytokine , transcription factor, cytokines produced and primary function for:
T- helper cell : 1 , 2 , 17, FH, reg
What is the T-helper cell 1 response?
> enhance phagocytosis and antigen presentation. Responses enhance inflammation
What is the T-helper cell 2 response?
> mediate defence which is independent of phagocytosis and directed against parasites
It doesn’t induce inflammation and promotes repair
What is the T-helper cell 17 response?
> response to pro-inflammatory cytokines early in an immune response
What is the T-helper cell reg response?
- Infection nears resolution > pathogen is removed > signal driving pro-inflammatory cytokine release disappears
- The tissue starts producing TGFβ.
-T cells enter the tissue > predominant cytokines drive them to become Tregs
- inhibit effector T cells and change macrophages to be anti-inflammatory
What are cytotoxic T cells ? How are naive cytotoxic T cells activated?
> Directly kill cells which express non-self antigen on MHCI
CD8 receptor binds with antigen on MHC1 and activates
Naive CD8+ T cells do not require costimulation for proliferation and differentiation into cytotoxic effector cells.
Dendritic cell needs help from CD4+ T cell to activate CD8+ T cell
IL-2 from T-helper cell acts on cytotoxic cell to allow to proliferate - clonal expansion
How do cytotoxic cells kill?
- The activated CD8+ cell enters the infected tissue and recognises the antigen bound to MHCI
- It contacts the cells and through binding of T Cell receptor to antigen and CD8+ to MHCI releases its granule contents.
- Perforin produces a pore in the surface of the infected cell and granzyme is released into it.
