Fibrinogen-like protein 2 (FGL2) mediates immune suppression in glioblastoma (GBM). Here, the authors show that FGL-2 expressed by GBM cancer cells acts by suppressing the differentiation of CD103+ DC cells required to activate the anti-tumor CD8+ T cell response via blocking GM-CSF signalling at NFKB, STAT1/5 and p38 level.