Figure 5.

CD4⁺ CD25^high T cells can suppress Vδ2⁺ T cells in the absence of TCR-αβ triggering. (a) Fluorescence-activated cell-sorted Vδ2⁺ T cells (2.5 × 10⁴ cells) isolated from tuberculin-skin-test-positive donors were stimulated with BrHPP (10 μm) plus interleukin-2 (IL-2; 25 U/ml) with or without purified protein derivative (PPD; 10 μg/ml) in the presence or absence of CD4⁺ CD25^high T cells (Tregs) at 1 : 1 effector : suppressor ratio. Interferon-γ (IFN-γ) in 5-day culture supernatants was determined by enzyme-linked immunosorbent assay. Mean values ± SEM are shown of triplicates of one representative experiment. (b) Percentage suppression was determined as follows: (IFN-γ in cultures with CD4⁺ CD25^high)/(IFN-γ in cultures without CD4⁺CD25^high) × 100. Means ± SEM of seven independent experiments are shown.