IL10 and central nervous system cancer: Glioma cells are poor antigen-presenting cells (APCs) for the immune system because of the downregulation in glioma cells of costimulatory molecules required to activate the immune system (Satoh et al, 1995), and the secretion by glioma cells of immunosuppressive cytokines such as transforming growth factor-β (TGF-β) (Constam et al, 1992), vascular endothelial growth factor (VEGF) (Gabrilovich et al, 1999), and interleukin (IL)-10 (Chen et al, 1994).