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Immuno CD8 T-cells Lecture Notes.docx

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Health Sciences
Jonathan Bramson

Lecture: CD8+ T-cells- The Third signal Naïve T-cell activation  During activation, you cannot just be activated by MHC peptide  Signal 1= MHC peptide complex (signal 1 not alone enough)  Signal 2= costimulation= happens mostly through CD28 (on T-cell) and B7- 1(CD80) and B7-2(CD86) (APC Ligand)  Only signal 1= anergy (tolerant T-cells that can give rise to regulatory T-cells) o Deals with a lot of the autoreactive T-cells  Only signal 2= no response  Up until here= primed Proliferation  Known as the expansion phase  Need rapid activation of the cells  T-cells go into effector function o By this point, they will only need signal 1 to function  Contraction phase= 70-90% of cells die through apoptosis  Not all die= will have some memory T-cells No infection= DCs will only provide signal 1 (no co-stimulatory molecule)  Will only generate anergic T-cells  Will undergo weak proliferation (not enough energy/signal) Infection  Presence of PAMPS  Bound to by DCs  Get costimilation (i.e. licensed)  Presence of signal 1 and signal 2= STRONG proliferation  Yields effector T-cells Coinhibitory Receptor  CD80/CD86  Yields CTLA-4 production o Decreases IL-2, anergy occurs, apoptosis  Naïve T-cells= only express CD28  Once activated= T-cells start to express CTLA-4 = susceptible to being primed Lecture: The Third Signal and CD4+ T-cells The third signal= cytokines= controls differentiation Eg. Interleukin= between leukocytes How do CD4+ Helper T-cells help with T-cell activation?  CD4+ T-cell help is required  APCs will FIRST activate your CD4+ t-cells  CD4+ t-cells in response to APCs will increase their CD40-L (ligand) and increase IL-2 = will then gen binding to APC CD40 on APC  Increase co-stimulatory molecules  APCs go onto activate more CD8+ T-c
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