Lecture 26 Flashcards
What does negative regulation involve?
Receptors, mechanisms, and cell types (Tregs)
How do Tregs dampen effect T cell responses (post infection)
Tregs release inhibitory cytokines
Pathways of Apoptosis
Intrinsic and Extrinsic pathways
What is the Intrinsic pathway of apoptosis
Death by neglect
T cell gets activated (signal 1 and 2)–>produce cytokines with transient receptors (IL2Ralpha) (impermanent)–>eventually signaling stops through these receptors–>lack of signaling = absence of survival signal–>apoptosis
What is the Extrinsic pathway of apoptosis
Rely on external source to initiate apoptosis
Triggered by Fas-FasL
involves CTLs
What causes activation on APC and T cells
B7.1 and B7.2 binding on antigen presenting cells = activation
CD28 binding on T cells = activation
What interaction causes negative regulation
CTLA4 interacting with B7.1 and B7.2 to block T cell activation
Examples of an inhibitory/regulatory receptors
CTLA4 and PD1
What receptor is expressed on Naive T cells
CD28
What receptors do T cells express 24 hours activation
CD28 AND CTLA-4 receptors (regulatory function to prevent overexpression of T cells)
Where is CTLA-4 found before post translational modification
Intracellularly
Where is CTLA-4 found after post translational modification
Phosphorylation allows CTLA-4 to be expressed on cell surface
Consequence of negative regulation by CTLA-4
Inhibit proliferation of T cells
Where is PD-1 expressed
On activated T cells
What does PD-1 bind to
PDL-1 (expressed on many cells) and PDL-2 (on APC during inflammation)
