Blood findings: morphologic, flow cytometric, and molecular studies. (A) The morphologic appearance of the “atypical” lymphoid cells is shown in the peripheral blood of the patient (magnification × 1000). (B) Six representative dot plots from the flow cytometric studies are shown. The population in green (population I) represents CD4⁺ T lymphocytes. The 3 subpopulations of CD8⁺ T lymphocytes (populations II, III, and IV) are represented in blue, black, and red, respectively. The regions drawn around populations in the sixth dot plot approximate the electronic gates used for flow-sorting the corresponding subsets. (C) Shown are the results from the TCR-γ PCR reactions performed on genomic DNA extracted from either bulk blood leukocytes or sorted populations of T cells (as indicated). The bottom row indicates a positive control PCR reaction (monoclonal TCR). TREC levels (per cell) from the corresponding populations are also indicated in the same panel to the right of each tracing.