CD8 count: ratio of helper-inducer T lymphocytes to cytotoxic-suppressor T lymphocytes in peripheral blood. T-cell subset analysis is performed by flow cytometry of lymphocytes after incubation with fluorescently tagged 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 people, the CD4:CD8 ratio ranges from 1.6-2.2.