| CD8 | <immunology> Differentiation antigens found on thymocytes and on cytotoxic and suppressor T-lymphocytes. Cd8 antigens are members of the immunoglobulin supergene family and are associative recognition elements in major histocompatibility complex class I-restricted interactions. (12 Dec 1998) |
|---|---|
| CD8 cell | <immunology> One type of T-lymphocyte which bears the CD8 molecular marker on its surface. Some CD8 cells recognise and kill cancerous cells and those infected by intracellular pathogens (some bacteria, viruses and mycoplasma). These cells are called cytotoxic T-lymphocytes (see). (09 Oct 1997) |
| CD8-positive T-lymphocytes | A critical subpopulation of regulatory T-lymphocytes involved in MHC class I-restricted interactions. They include both cytotoxic T-lymphocytes (T-lymphocytes, cytotoxic) and suppressor T-lymphocytes (T-lymphocytes, suppressor-effector). (12 Dec 1998) |
| CD80 | <immunology> The natural ligand for the T-cell antigen CD28 (antigens, CD28) mediating t-cell and B-cell adhesion. Cd80 is expressed on activated B-cells and gamma-interferon-stimulated monocytes. The binding of CD80 to CD28 and ctla-4 provides a co-stimulatory signal to T-cells and leads to greatly upregulated lymphokine production. (12 Dec 1998) |
| antigens, CD8 | <immunology> Differentiation antigens found on thymocytes and on cytotoxic and suppressor T-lymphocytes. Cd8 antigens are members of the immunoglobulin supergene family and are associative recognition elements in major histocompatibility complex class I-restricted interactions. (12 Dec 1998) |
|---|---|
| CD4/CD8 count | The ratio of the number of helper-inducer T lymphocytes to cytotoxic-suppressor T lymphocytes, as measured by monoclonal antibodies to the CD4 surface antigen found on helper-inducer T-cells, and the CD8 surface antigen found on cytotoxic-suppressor T-cells. In healthy individuals, the H/S ratio ranges between 1.6 and 2.2.When the body mounts an immune response, as against a virus or a transplant, the ratio is almost always reduced because of a decrease in the number of circulating helper-inducer cells and an increase in suppressor cells. The CD4/CD8 count has been used to monitor for signs of organ rejection after transplants, and more recently has become a tool for assessing the relative condition of HIV patients. With the CD4 absolute count and the CD4 lymphocyte percentage, it provides a way of gauging the progression from HIV to AIDS. (05 Mar 2000) |
| CD4:CD8 ratio | The ratio of CD4 to CD8 cells. A common measure of immune system status that is around two in healthy individuals. The ratio of T-lymphocytes that express the CD4 antigen to those that express the CD8 antigen. This value is commonly assessed in the diagnosis and staging of diseases affecting the immune system including HIV infection. (12 Dec 1998) |