Enhanced expression of PD-1 ligands in acute GVHD. Lethally irradiated BALB/c recipients were given 107 B6 BM cells alone or with 2 × 106 B6 T-cells. Immunofluorescence staining was performed on day 7 (A), day 14 (B), and day 21 (C) for PD-L1 and PD-L2 (4 mice/group). Images were captured at ×200 magnification, using an Olympus FluoView 500 or Olympus FluoView 1000 BX2 confocal laser scanning microscope and analyzed with Adobe Photoshop CS3 (version 10) for determination of the relative fluorescence staining intensity. Data are representative of 2 independent experiments. *P < .05; **P < .01; ***P < .001.