University:
York University
Course:
SC/BIOL 3120 | Immunobiology
Academic year:

2023
Views:

370

Pages:

2
Author:

Niklas

CTL Phase 1: Activation and Generation Naive CTL (CTL-P) must be activated. Activation of CD4+ and CD8+ T cells require the same three signals: TCR Costimulatory signals Cytokines Antigen presentation: Used to think it was sequential, but it's not. Stimulation of naive T cell: MHC class I or II CD4+ or CD8+ T cell Costimulatory molecules Proliferation of T cell: Clonal expansion Differentiation of T cell: Effector function Apoptosis vs Necrosis: Apoptosis: Phagocytosis of apoptotic cells and fragments Necrosis: Enzymatic digestion/leakage of cellular contents We would rather induce apoptosis than necrosis because necrosis would lyse the cell and spill out all the "bad" stuff. Inducing Apoptosis Fas/FasL: Fas expressed on the target cell FasL expressed on the CTL When they bind together, apoptosis is induced. How do CTLs kill? CTLs induce the cell to undergo apoptosis: Fas/FasL interaction Directional release/injection of granzymes and perforins Perforin and Granzyme B: Perforin: They perforate Make tiny holes in the cell Gets rid of membrane potential and the osmotic differences across the cell - cells cannot survive this way Also allows entry of granzymes Granzyme B: Induces apoptosis via DNA fragmentation Activate apoptotic pathways that result in the cell's DNA cutting itself up Target cells undergo apoptosis via the caspase signaling cascade.