The CD8 antigen, also known as T8 or Leu2 or Lyt2 or T cell coreceptor, is a cell surface glycoprotein as a dimer with a molecular mass of 32 KD. It is found on most cytotoxic T lymphocytes that mediates efficient cell-cell interactions within the immune system. The CD8 antigen acts as a coreceptor with the T-cell receptor on the T lymphocyte to recognize antigens displayed by an antigen presenting cell in the context of class I MHC molecules. The T8 antigen is expressed by the suppressor/cytotoxic subset of T lymphocytes which comprise most of the cortical thymocytes and approximately 30% of peripheral blood T cells. Studies have demonstRated that increased levels of T8+ cells are associated with viral infections such as hepatitis B, Epstein-Barr, and cytomegalovirus. This Antibody may be used in the study of cell-mediated cytotoxicity and that of immunoregulation and T-lymphocyte-mediated suppression. This Antibody stains CD8 (T8) antigen suppressor/cytotoxic T lymphocytes and majority of thymocytes (approximately 80%) in frozen tissue sections.