Figure 4. Human γδ Treg cells induce DC senescence.

(A) γδ Treg cell treatment markedly up-regulated SA-β-Gal expression on DCs. DCs cultured in medium only or co-cultured with CD4-C1 effector T cells had little SA-β-Gal expression. Immature DCs were incubated alone or co-cultured with γδ Treg or CD4-C1 T cells at a ratio of 5:1 in the presence of GM-CSF, IL-4 and TNF-α for 2 days. The treated DCs were purified and SA-β-Gal expression determined. Results shown in the right panel are mean ± SD from three independent experiments. **p<0.01, compared with the medium only and CD4-C1 treatment groups. (B) Decreased expression of CD83, CD80, CD86 and HLA-DR and upregulation of PD-L1 in DCs treated with γδ Treg cells. Cell treatment and procedure were the same as in (A). All these markers were analyzed by FACS. (C) Senescent DCs induced by γδ Treg cells dominantly existed in the CD80^low cell populations. Furthermore, CD80^low cell populations purified from Treg-treated DCs showed increased PD-L1 expression. Cell treatment and procedure were the same as in (A). γδ Treg-treated DCs expressing CD80 were sorted by FACS. SA-β-Gal and PD-L1 expression in CD80^hi and CD80^lo cell populations purified from γδ Treg-treated DCs were determined. Results shown in the right panel are mean ± SD from three independent experiments. **p<0.01, compared with the CD80^hi group.