Fig. S4.

Activin-A suppresses anti-CD3–driven human T-cell responses in an APC-free system. (A, Left) Human naive CD4⁺ T cells were stimulated with anti-CD3/CD28 antibodies in the presence of activin-A (act-A–iTr1 cells) or PBS (Tconv cells) for 7 d. (A, Right) Tconv or act-A–iTr1 cells were isolated from primary induction cultures and restimulated with anti-CD3/CD28 antibodies for another 7 d. ³[H]Thymidine incorporation is depicted. Data shown are mean ± SEM of triplicate wells and are pooled from n = 4 independent experiments (n = 4 donors). (B) Representative FACS plots showing IL-10–expressing cells, gated on CD4⁺ T cells, stimulated as above. Data represent n = 4 independent experiments (n = 4 donors). Statistical significance was obtained by the Student’s t test (*P < 0.05; ***P < 0.001).