Regulation of the T-cell response is a very fine-tuned process designed to initiate an immune-response when a threat is detected, and to terminate it when the threat has been eliminated. At the heart of practically every conventional T-cell response, takes place a two step signalling process that dictates the T-cell fate. The first signal is the interaction between the T-cell receptor (TCR) and the peptide-major histocompatibility complex (pMHC) expressed on the surface of most cell types, which creates an interface between the T-cell and the target cell. This interface is further stabilised by secondary signals delivered by a number of accessory molecules. For example, The co-stimulatory molecule CD28 can bind CD80 and result in T-cell activation, or bind CTLA-4 and abrogate the T-cell response.
T-cell activation is a critical event for the initiation and regulation of the immune response, initiating and intra-cellular signalling cascade that results in proliferation and triggering of effector functions. An extensive number of molecules are involved in this process, some of which have not yet been fully characterised. Next, you’ll find a description of the main well characterised elements involved in the activation of a CD8+ T lymphocyte