PD-L1 blockade unleashes the development of IL-4-producing Th2 cells.
(A) Development of effector cells expressing T-bet or GATA3. Purified CD4+ CD62L+ DO11.10 T cells were stimulated with OVA323-339 (1 μg/ml) in a Th1 or Th2-skewing condition. Intracellular staining for T-bet and GATA3 expression was performed after 1 and 4 days. (B, C) PD-1-dependent regulation of Th1 and Th2 cell differentiation. Naïve DO11.10 T cells were stimulated in the neutral condition (B) or Th1/Th2-skewing conditions (C) for 3 days using PD-L1-deficient or PD-L1-expressing parental A20 cells as APC. Subsequently, cytokine-producing activities were evaluated by stimulating activated T cells (1.5 x 105 cells) with immobilized anti-CD3 mAb for 24 h. (D-J) Naïve DO11.10 T cells were stimulated for 3 days using parental A20 cells as APC in the presence or absence of anti-PD-L1 mAb. T cell stimulation was conducted in the neutral (D-F) or skewing condition for Th1 (G, H) and Th2 cells (I, J). Activated T cells were restimulated in the same condition for 2 more days. Intracellular staining for cytokines was performed on day 5. Percentages of IFN-γ- and IL-4- positive events in CD4+ cells (D, E, G-J) and IL-4+ event / IFN-γ+ event ratios in individual samples (F) are shown. Data represent average ± SEM of triplicate (B, C) or quadruplicate (E, F, H, J) samples. *p < 0.05, ***p < 0.001; Student’s t-test.