Expression of IL-2Rα, IL-2Rβ, and IL-2Rγ by CD8 T lymphocytes. (A) PBMC from blood collected on heparin were treated by MoAbs 33B3, CF1, and 3B5. Further characterization of the population was achieved by treatment with anti-CD3 and anti-CD28 MoAbs. FITC-labeled Fab fragment anti-IgG was used, followed by PE-conjugated anti-CD8 MoAb. Quadrant setting distinguishing positive immunofluorescence from background fluorescence was determined by staining with isotype-matched control MoAbs. The percentage of positive cells for the different markers is indicated. (B) Staining and analysis was performed as in (A). The percentage of positive cells for the different markers is shown for a group of nine individuals.