Pro-tumor immunity of OX40 signaling. a. The expression of OX40L mRNA was induced in A172 glioblastoma cells under hypoxia (*P < 0.05). b. Representative immunohistochemistry of OX40L protein in A172 cells. Under hypoxia (left panel), under normoxia (right panel). Scale bar, 40 μm. c. Numbers of OX40L positive cells/ total cells, counted under 200× magnification (mean ± SEM, *P < 0.05). The data are shown as % positive cells per total cells. d. Production of IL-10 protein from mouse Treg cells, as determined by ELISA (n = 5) (mean ± SEM, *P < 0.05).