Figure 6.

Mechanisms of regulatory T cell (Treg)-mediated suppression of γδ T-cell proliferation. (a) Peripheral blood mononuclear cells (PBMC) were incubated with bromohydrinpyrophosphate (BrHPP, 1 μm) or medium alone and co-cultured with autologous purified Tregs separated by semi-permeable membranes (Transwells) or with supernatant (SN) from overnight-cultivated and interleukin (IL)-2-stimulated Tregs. (b) Supernatants were heated for 15 min at 56° or 99°, or treated with proteinase K (2 hr at 37°). (c) PBMC incubated with BrHPP were co-cultured with supernatant from overnight-cultivated Tregs alone or treated with 1-methyl-l-tryptophan (1·5 mm), N^G-monomethyl-l-arginine (l-NMMA; 2 mm) or N^ω-hydroxy-nor-l-arginine (nor-NOHA; 0·5 mm) at ratio 1 : 1 and proliferation of γδ T cells was analysed on day 7 by flow cytometry. Each bar represents mean values ± standard deviation of triplicate cultures from one healthy donor and is representative of four independent experiments.