The phenotype of the CD8^dull subsets determined by eight-color flow cytometry. Shown is one subject who was treated for HD 22 years before analysis and has elevated levels of both the CD8^dullCD4⁺ subset (top panels) and the CD8^dullCD4⁻subset (middle panels). The CD8^bright subset from this subject is shown in the lower panels for comparison. The panel on the left has been gated first on lymphocytes using forward and side scatter and then on T cells using CD3. The gates for the CD8^dull and CD8^bright subsets are shown in this panel. Surface marker expression measured from three different eight-color antibody combinations are shown (see Materials and Methods). The percentages of cells within the indicated subset that express the marker are shown. Bivariate data is shown as 5% probability contour plots with outlying events shown as dots.