The CD8 antigen, also known as cluster of differentiation 8, refers to a glycoprotein present on the cell surface that consists of two distinct subunits, designated as alpha and beta. An antibody against CD8 serves as a T-cell marker utilized for identifying cytotoxic or suppressor lymphocytes. Moreover, the presence of CD8 can be observed in natural killer cells, specific thymocytes, certain null cells, and cells originating from the bone marrow. This particular antibody, when used alongside other markers, aids in differentiating between T-cells that are either reactive or neoplastic in nature. It has been observed that CD8 expression is absent in cases of Mycosis Fungoides. In infrequent instances, anti-CD8 antibodies may bind to neoplasms of non-hematolymphoid origin.