T Lymphocyte Activation Test II Flashcards
How are Ags transported to LN from periphery?
By mature activated DC’s
What two steps can occur after T cells are activated and differentiate into effector cells?
- Remain in lymphoid organs to help B lymphocytes
2. Migrate to sites of infection to help activate macrophages
What chemokine is secreted after Ag recognition by T cells, along with clonal expansion?
IL-2
How do effector CD8+ CTLs function?
By killing infected and altered host cells
What responses are induced by Ag recognition accompanied by co-stimulation in T cells?
Secretion of cytokines
Proliferation (Clonal exp.) IL-2 needed
Differentiation into effector and memory cells
What three signals are required for proliferation and differentiation of T cells?
Ag recognition
Costimuolation
Cytokines
What kind of signal does CD28:CTLA4 give?
Inhibitory-
What kind of signal does CD28:CD80/86 give?
costimulatory signal
What does CD2:CD48/59 do?
adhesion with APC’s
What does LFA1:ICAM1 do?
adhesion with APC’s
What is significant about Bacterial superantigens SAgs?
They are potent activators of T cells without co stimulatory signals. They are the exception to the fact that Ag recognition by TCR alone doesn’t stimulate clonal expansion of naive T cell.
How do SAgs work?
SAgs glue T cells to the APC’s for a prolonged amount of time activating T cells and inducing robust proliferation of SAgs activated T cells and produce massive amounts of IFN-y that activates Macro. to overproduce TNF and IL-1 which leads to shock.
Where do SAgs bind?
Simultaneously bind MHC class II molecules outside the peptide binding groove and V region of the beta subunit of the TCT
What happens to T cells if they recognize an Ag but without costimulation?
They may become anergic
What activates DC’s to express costimulators such as CD80/86 and what does that do?
Microbes and cytokines produced during innate response.
Provides costimulatory signal two making APC’s capable of activating naive t cells
Activated DC’s produce what cytokine and what is its role in costimulation of T cell activation?
IL-12 (signal 3) which stimulates differentiation of naive T cells into effector cells
Describe T cell costimulation by CD28?
It binds the costimulatory molecules B7-1 (CD80) and B7-2 (CD86) which are expressed on activated APC’s
How are T cell responses regulated?
The expression of B7 is regulated by CD28 inhibitory or activating proteins.
What type of cells express ligands such as B7 family?
APC’s
What type of cells express receptors such as CD28,CTLA-4, ICOS and PD-1?
T cells
Describe CD28?
Expressed constitutively on T cells.
Costimulation of naive T cells and generation of T reg cells is major function.
Binds with CD80/86 (B7-1 and B7-2)