Regulatory/suppressive functions of CD4⁺HLA-G1^acq+ T cells. The regulatory function of CD4⁺HLA-G1^acq+ T cells was investigated by adding them as irradiated third-party cells in functional assays. (A) Irradiated CD4⁺HLA-G1^acq− and CD4⁺HLA-G1^acq+ T cells were added to mixed-lymphocyte reactions between autologous PBMCs and allogeneic LCL-RSV cells. When indicated, HLA-G1 was masked at the CD4⁺HLA-G1^acq+ T cells by blocking anti–HLA-G1 mAb. CD4⁺HLA-G1^acq+ but not CD4⁺HLA-G1^acq− T cells inhibited resting T-cell allo-proliferation. This inhibition was abrogated by blocking anti–HLA-G1 mAb. Results shown are representative of 5 independent experiments. (B) Irradiated CD4⁺HLA-G1^acq− and CD4⁺HLA-G1^acq+ T cells were added to mixed-lymphocyte reactions between autologous PBMCs and allogeneic LCL-RSV cells at different third-party–responder–stimulator ratios. Inhibition of resting T-cell allo-response was directly proportional to the amount of CD4⁺HLA-G1^acq+ used. Results shown are representative of 3 independent experiments.