Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
Cytotoxic T lymphocytes (CTLs) are a type of white blood cell that directly kill infected or cancerous cells. They recognize their targets through specific antigens presented by MHC class I molecules on the surface of these cells.
5 Must Know Facts For Your Next Test
CTLs are also known as CD8+ T cells due to the presence of the CD8 glycoprotein on their surface.
CTL activation requires two signals: recognition of antigen-MHC class I complex and costimulatory signals from helper T cells.
Once activated, CTLs release perforin and granzymes to induce apoptosis in target cells.
CTLs play a crucial role in controlling viral infections and tumor surveillance.
Memory CTLs can quickly respond to previously encountered antigens, providing long-term immunity.
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Related terms
Helper T Cells: A type of T cell that assists other immune cells by releasing cytokines and providing necessary signals.
MHC Class I: Molecules found on almost all nucleated cells that present antigenic peptides to CD8+ T cells.
Apoptosis: The process of programmed cell death that eliminates damaged or infected cells without causing inflammation.