Flashcards in Activation Of T Lymphocytes Deck (71)
Activated T cells differentiate into effector cells. What are the two fates of the effector cells?
Remain in the lymphoid organs to help B lymphocytes
Migrate to sites of infection to help activate macrophages.
What cytokine is secreted as Ags are recognized by T cells?
This results in clonal expansion as a result of proliferation and differentiation of the T cells into effector or memory cells.
How do effector CD4 T cells respond to Ags?
They produce cytokines that have several actions, such as the recruitment and activation of leukocytes and activation of B cells.
What is the function of effector CD8 CTLs?
They kill infected and altered host cells.
What three things ocur when Ag recognition and other activating stimuli induce responses in T cells?
Secretion of cytokines
Proliferation (clonal expansion)
Differentiation into effector and memory cells.
What are the functions of effector T cells?
To perform functions that are responsible for the elimination of microbes, and in disease states, for tissue damage.
What occurs to T cell responses after the Ag is eliminated?
T cell responses decline.
What are the three signals needed for the proliferation of T lymphocytes and their differentiation into effector and memory cells?
What is required for the activation of naive T cells?
Ag presented by DCs.
The effector T cells can recognize Ags presented by tissue macrophages and B cells.
What results from the activation of PLC1?
The production of IP3 and DAG.
What occurs from the production of IP3?
Increases of cytosolic free calcium
What does T cell receptor signaling overall result in?
The activation of Ras and MAPK, which activate transcription factors such as NFAT and NF-KB.
What do superantigens bind to?
To MHC class II molecules and the V region of the beta subunit of the TCR.
What occurs to T cells upon superantigen acitvation?
T cells produce massive amounts of cytokines which may lead to shock.
How do superantigens (SAgs) bind to TCR?
Via the variable region of the beta chain.
When activated APCs are present, what is there increased expression of?
Costimulators, as well as the secretion of cytokine IL-2
What are the three signals required in costimulation in T cell activation?
Inflammation and activation of costimulators (B7)
Production of cytokiens of IL-12
What results from increased secretion of IL-2 or expression of IL-2R?
What is the best characterized costimulatory pathway in T cell activation?
T cell surface receptor CD 28, which binds co stimulatory molecules B7-1 and B7-2 (CD80 and CD86).
These are expressed on activated APCs
What is the function of B7 costimulators?
It ensures that T lymphocyte responses are initiated only wheen needed.
What is the result of CD28 and Ag recognition?
The survival, proliferation and differentiation of specific T cells.
How is T cell activation influenced?
It is influenced by a balance between engagement of activating and inhibitory receptors of the CD28 family.
What is the result of CD28 and B7-1?
Costimulationof naive T cells; generation of regulatory T cells.
What is the function of B7-2 and CTLA-4?
Negative regulation of immune responses; self-tolerance
Where are B7-1 and B7-2 found?
DCs, macrophages and B cells.
Where are CD28, CTLA-4, iCOS and PD-1 found?
On T cells
What is the function of iCOS?
Costimulatio nof effector and regulatory T cells; generation of follicular helper T cells.
What is the function of CD274 and CD273 & PD-1?
Negative regulation of T cells.
When is CTLA4-mediated immune checkpoint induced in naive T cells?
At the time of their initial response to Ag.