CD8+ T cells Flashcards
What is the main function of CD8+ T cells?
To recognize and destroy infected or abnormal cells through antigen-specific cytotoxicity
What molecules do CD8+ T cells recognize?
MHC Class I molecules presenting peptides from endogenous antigens
How do CD8+ T cells avoid harming uninfected cells?
They specifically target only cells presenting antigens on MHC Class I and leave neighboring cells unharmed
What is the role of the immunological synapse in CD8+ T cell function?
It is the interface between the CD8+ T cell and the target cell where granules are released to induce apoptosis
What are the key effector molecules in CD8+ T cells?
Perforin granzymes and Fas ligand
What is the role of perforin in CD8+ T cell killing?
Perforin forms pores in the target cell membrane to allow entry of granzymes
What is the role of granzymes in CD8+ T cell killing?
Granzymes enter the target cell and activate caspases leading to apoptosis
What is the role of Fas ligand on CD8+ T cells?
Fas ligand interacts with Fas receptors on target cells to trigger the extrinsic apoptosis pathway
What are the two pathways of apoptosis triggered by CD8+ T cells?
The intrinsic mitochondrial pathway and the extrinsic Fas-dependent pathway
How is the intrinsic pathway of apoptosis activated?
CD8+ T cells release granzymes that activate pro-apoptotic proteins leading to cytochrome c release from mitochondria
How is the extrinsic pathway of apoptosis activated?
Fas ligand on CD8+ T cells binds to Fas receptors on target cells activating pro-caspase 8
What happens after cytochrome c is released from mitochondria during apoptosis?
Cytochrome c activates apoptotic protease activating factor 1 Apaf-1 and caspase-9 leading to cell death
What are the key features of CD8+ T cell-mediated killing?
Antigen specificity rapid apoptosis induction and the ability to target multiple infected cells sequentially
What are gd T cells?
A subset of T cells with limited TCR diversity that recognize non-peptide antigens without MHC restriction
Where are gd T cells mainly found?
In epithelial tissues as intraepithelial lymphocytes
What are invariant NKT iNKT cells?
A type of innate-like lymphocyte that recognizes glycolipid antigens presented by CD1d molecules
What are MAIT cells?
Mucosal-associated invariant T cells that respond to bacterially derived folate metabolites presented by MR1 molecules
What is the significance of MAIT cells in immunity?
They are abundant in mucosal tissues like the gut and liver and play a role in the mucosal immune system
How do iNKT cells differ from classical T cells?
They have limited TCR diversity and recognize microbial glycolipids rather than peptides
What is the role of sentinel proteins like p53 in apoptosis?
They detect cellular stress and activate pro-apoptotic pathways in response to CD8+ T cell signals
How do CD8+ T cells contribute to adaptive immunity?
By eliminating infected cells and preventing pathogen replication they reduce the antigen load for other immune responses
What is the difference between perforin-dependent and Fas-dependent killing by CD8+ T cells?
Perforin-dependent killing involves granules while Fas-dependent killing relies on Fas-Fas ligand interactions
