| T lymphocytes (T cells) play critical roles in the regulation of immune responses, and are responsible for mediating many of the effective mechanisms of the immune system. One of the most important actions of T cells is to lyse the cells expressing specific antigens. Most cells with such cytotoxic activity are CD8+ T cells called cytotoxic T lymphocytes (CTLs). CTLs carry out important effector functions, being one of the cell types that are responsible for destroying virally, bacterial and parasitic infected cells, tumour cells, and allogeneic transplant cells. CTLs recognize foreign antigens that have been processed intracellularly and expressed as peptide fragments in association with HLA class I molecules on the surface of antigen presenting cells (APCs). The importance of CTLs in the recovery and establishment of protective immunity from viral and bacterial infection has been documented in both animal models and natural infections in human being. The development of biotechnology has led to a dramatic increase in the number of novel immunotherapeutics for the treatment of cancer, autoimmune disorders and infectious diseases. These increasing activities in the field of immunotherapy, coupled with the expense of clinical trials, have led to renewed interest in methods that accurately assess CTLs numbers and function. Researchers seek to maximize the amount of information about CTLs that can be obtained from both clinics and laboratories. Assessing the quantitative and qualitative nature of a CTL response, for example, following vaccination or immunosuppressive therapy, can provide valuable information about the efficacy of a treatment, in place of a clinical endpoint.Biochemical studies of TCR-ligand interactions have revealed relatively weak affinities (10-4-10-7M). Moreover, the off-rate of the interactions seems to be particularly fast, with a half-life of only a few seconds. So far, four types of assays to... |
