Lecture 16 (Linking) Flashcards
What happens when Signal 1 and Signal 2 are activated in T cells?
They lead to the production of IL-2, which induces robust T-cell proliferation.
Why is IL-2 considered an example of an autocrine cytokine response?
T cells produce both the IL-2 cytokine and its receptor, enabling self-stimulation and proliferation.
What is the role of IL-2 binding to its receptor?
Binding induces a very strong proliferation signal during T-cell activation.
What is the outcome of IL-2-induced proliferation in T cells?
Activation and robust proliferation result in the production of memory (M) and effector (E) clonal cell populations.
What is the result of Signal 1 (TCR) and Signal 2 (CD28) convergence in T cells?
Activation of transcription of the IL-2 gene (cytokine) and IL-2Rα gene (CD25, part of the receptor).
Is IL-2Rα expressed at baseline?
No, IL-2Rα is not expressed at baseline and is transcribed only after Signal 1 & 2 activation.
What is the difference in IL-2 receptor affinity with and without IL-2Rα?
(1) Without IL-2Rα: The IL-2Rβ and IL-2Rγ chains have low affinity for IL-2.
(2) With IL-2Rα: The receptor has a much higher affinity for IL-2.
How are the transcription of IL-2 and IL-2Rα genes regulated?
They are two separate genes, and their transcription is regulated differently.
What is required to activate transcription factors for IL-2 and IL-2Rα genes?
Signal 1 (TCR) and Signal 2 (CD28) initiate a downstream signaling cascade that activates transcription factors.
Do resting/naïve T cells produce IL-2 or express IL-2Rα?
No, resting/naïve T cells do not produce IL-2 or express IL-2Rα.
What happens when T cells receive Signal 1 & 2?
1) Transcription of IL-2 and IL-2Rα genes occurs.
2) IL-2 is secreted.
3) High-affinity IL-2 receptors are expressed on the cell surface.
How does IL-2 act on T cells?
(1) Autocrine: IL-2 binds to its own receptor on the same T cell.
(2) Paracrine: IL-2 can bind IL-2 receptors on regulatory T cells (Tregs), which act as a “sink” to limit IL-2 availability.
Do Tregs produce IL-2?
No, Tregs do not produce IL-2 but have the IL-2Rα chain on their receptor to capture IL-2 from the environment.
What is the result of IL-2 receptor signaling in T cells?
It promotes proliferation and helps modulate T-cell differentiation for some subsets.
