Cytotoxic T cells are a key part of the cellular immune response, killing cells that display foreign antigen on their surface, primarily virus-infected cells. Transformed cells can also be detected and eliminated by cytotoxic T cells. There are two mechanisms by which activated cytotoxic T cells kill cells presenting specific antigen. One method involves the release of secretory granules containing perforin and granzyme to induce lysis of the targeted cell. Cytotoxic T cells also express Fas ligand to bind to Fas on target cells and induce apoptosis. Communication with and interaction with other cell types is essential for cytotoxic T cell function. Distinct types of T cells are characterized and their activities determined by the proteins they express on their cell surface. Cytotoxic T cells will only respond to antigen presented on the surface of cells bound to MHC I proteins, not antigens present in solution. The T cell receptor, with the multiprotein CD3 complex, is responsible for the recognition of specific antigens, triggering the activation and proliferation of cells. Cytotoxic T cell activation also requires additional signals provided by helper T cells in addition to signals provided by antigen-presenting cells. Thy1 provides a general marker of T cells, and the presence of CD8 protein that binds to MHC distinguishes cytotoxic T cells from CD4 positive helper T cells. CD28 expressed by T cells acts as a costimulatory signal with the T cell receptor when it binds its ligand, a B-7 coreceptor, on antigen-presenting cells. Inappropriate regulation of the costimulatory signal can lead to too great or too small of an immune response. Interaction of activated cytotoxic T cells is aided by increased expression of LFA-1, a cell-adhesion molecule that binds to ICAM on target cells. CD2 is a T cell adhesion molecule. Mice with a disrupted CD2 gene are largely normal and appear to have a normal immune system, but CD2 on cytotoxic T cells may assist in interaction with target cells.
7.0: Changed members. Upgraded to final version of Biocarta.
License Terms for BioCarta data in MSigDB
MSigDB gene sets derived from BioCarta pathways are protected by copyright, (c) 2000-2017 BioCarta, all rights reserved. They are provided
under license to the Broad Institute, Inc. with qualified permission to include in this release, subject to Biocarta's
"Disclaimer
of Liability and of Warranties" (formerly found at www.biocarta.com). Inclusion of these gene
sets is conditioned upon acknowledgment and retention of the aforementioned copyright, and agreement to such disclaimer. The BioCarta
derived gene sets are in the MSigDB C2 and M2 collections, and can be recognized by the "BIOCARTA_" prefix in their name.
