Consistent with a pro-tumor role of IL-6 in alternative Mφs polarization, we here show that targeting IL-6 by genetic ablation or pharmacological inhibition moderately improves T-cell infiltration into GBM and enhances mouse survival; however, IL-6 inhibition does not synergize PD-1 and CTLA-4 checkpoint blockade. Here, CTLA4 is linked to glioblastoma.