7 Helper T-cells and Cytokines Flashcards
Describe the different types of T-helper cells
T-Helper 1
- help macrophage intracellularly digest better
T-Helper 2
- help B-cells produce antibodies
Th17
- helps in inflammatory response
Th Reg
- helps in dampening down of the immune response
Describe Cytokines
They are secreted proteins
- which regulate the amplitude and the duration of immune + inflammatory responses
They are small
- usually produced by T-cells transiently and locally
- so, when and where needed
- are extremely potent
They bind to specific cell-surface receptors + trigger intracellular pathways
- change cell behaviour
Describe the action of cytokines
Cytokine binds to receptor
- Receptor clusters
- Signalling events take place
- This changes the behaviour of the cell whch cytokine is bound
> Phosphorylated transcription factors (by clustering of the cell receptor) move into the nucleus to initiate gene transcription
List some examples of Cytokines
Cytokines include:
- Interleukins (IL-1, IL-2 etc.)
- Tumour necrosis factor (TNF-a, y, ß)
- Colony-stimulating factor (G-CSF)
- Chemokines (help cells move, via chemotaxis)
How can cytokines influence which type of T helper cell we get?
Interaction between CD4 receptor and MHC Class II
- CD4 helper T cell produces cytokines (at the time of interaction) - type of cytokine released matters
A CD4(0) cell is a CD4+ cell - not differentiated
- At T cell activation, the polarising signal will determine what type of CD4 T Helper cell is generated
- this determines on the cytokines present in the microenvironment at the time of T cell activation)
Which cytokines stimulate the proliferation of different T-Helper Cell types
Th1 (help macrophage)
- IL-12, IFN-y
Th2 (help B cell)
- IL-4
TH17 (help inflammatory response)
- IL-6, TGF-ß, IL-23
Th Reg (helps to dampen down of immune response) - IL-10, IFN-a, TGF-ß
NOTE:
- cytokines which produce Th1 will inhibit Th2
- vice versa
Describe how Th2 is related to B-cell activation
- Pathogen enters the body
- Taken up by dendritic cell
- Processed and presented on MHC Class II
- Cytokine microenvironment is IL-1 = Th2 cell
- Th2 cell produces cytokines e.g. IL-4
At the same time
- B-cells are directly recognising the same pathogen
- and binding to it, processing it and presenting it to MHC Class II
- to a T-cell receptor
Th2 cells then can secrete cytokines
- to help B-cell produce antibodies against the original target
Where does the B-cell activation by Th2 cells take place?
Not in the tissues - in the local Lymph Organs (nodes)
- Once dendritic cells have phagocytosed the pathogen, the antigen is carried to lymphoid tissue
- Activating specific T and B cells and antibody production
- recirculation to the site of infection
Describe the events that take place from a pathogen entering by a cut in the hand
include movements of pathogen information
location of B and T cell activation
and how they return back
Pathogen enters tissue
APC and pathogen information leaves the tissue via afferent lymphatics and goes to lymph nodes
B and T cells enter the lymph nodes from blood circulation
The lymph node is the ‘hub’ - where pathogen info meets the naive B and T cells
- so correct B and T cells are activated in Paracortx
Once activated, B and T cells leave the lymph node via efferent lymphatics
and enter back into the circulation via the thoracic duct
Back to the site of infection to carry out effector functions
When the cell activates B-cell
- it generates the Germinal centre (from the primary follicle)
Describe how the activated T and B cells are able to make it back to the site of infection from the lymph node cortex
This is enabled by the fact that cells express adhesion molecules on their cell surface
- This ‘tissue homing’ of activated lymphocytes - the expression of adhesion molecules, integrins, and chemokine receptors
NOTE:
Chemokine: small cytokine, determined by the ability to induce chemotaxis in nearby responsive cells
Chemotaxis: move to areas of higher [chemokine]
