C1S and neoplasm: In the reactive astrocytes from the tumor we identified an increased expression of immune associated genes such as CHI3L1, HLA-DRA, CD274, HLA-DRB3, CD37 (Fig. 1b), as well as genes that contributed to proliferation (MKI67, ANXA2) and complement components (C1S, C1R) (Fig. 1b and Supplementary Fig. 2).