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Antigen presentation stimulates T cells to become either "cytotoxic" CD8+ cells or "helper" CD4+ cells.. A cytotoxic T cell (also known as T C, cytotoxic T lymphocyte, CTL, T-killer cell, cytolytic T cell, CD8 + T-cell or killer T cell) is a T lymphocyte (a type of white blood cell) that kills cancer cells, cells that are infected by intracellular pathogens (such as viruses or bacteria), or ...
Once activated, these cells can perform functions ascribed to both helper and cytotoxic T cells: cytokine production and release of cytolytic/cell killing molecules. They are also able to recognize and eliminate some tumor cells and cells infected with herpes viruses.
Activated effector T cells can be placed into three functioning classes, detecting peptide antigens originating from various types of pathogen: The first class being 1) Cytotoxic T cells, which kill infected target cells by apoptosis without using cytokines, 2) T h 1 cells, which primarily function to activate macrophages, and 3) T h 2 cells ...
In 1991, three groups reported discovering CD154, which is the molecular basis of T cell helper function. Seth Lederman at Columbia University generated a murine monoclonal antibody, 5c8 that inhibited contact-dependent T cell helper function in human cells which characterized the 32 kDa surface protein transiently expressed on CD4 + T cells. [16]
After vaccine induced activation, dendritic cells are able to migrate to lymph nodes and activate CD4+ T helper cells as well as cross prime CD8+ T cytotoxic cells. This mass generation of activated tumor specific CD8+ T cells increases anti-tumor immunity, and is also able to overcome many of the immune suppressive effects of tumor cells. [10]
Only licensed dendritic cells are able to activate cytotoxic T cells. T cell licensing of dendritic cells is key for activation of cytotoxic T cells for many pathogens, although the extent to which T cell help is needed may vary. [14] In MHC class I and class II molecules, only certain epitopes of an internalized peptide can be presented.
CD3 (cluster of differentiation 3) is a protein complex and T cell co-receptor that is involved in activating both the cytotoxic T cell (CD8+ naive T cells) and T helper cells (CD4+ naive T cells). [1] It is composed of four distinct chains. In mammals, the complex contains a CD3γ chain, a CD3δ chain, and two CD3ε chains.
Upon binding to pMHC, the TCR initiates a signaling cascade, involving transcription factor activation and cytoskeletal remodeling resulting in T-cell activation. Active T cells secrete cytokines, undergo rapid proliferation, have cytotoxic activity and differentiate into effector and memory cells.