Strategy of NK-cell gating within total freshly purified PBMCs. (A) Within the lymphocyte gate of freshly purified PBMCs, NK-cell subsets were separated from CD14⁺ (monocytes), CD3⁺ (T lymphocytes), and CD19⁺ (B lymphocytes), and then characterized for CD56 and CD16 surface expression. (B) Representative flow cytometric example of expansion of CD56⁻/CD16⁺ NK-cell (lower right) subset from a chronic viremic HIV-1–infected patient.