In an effort to address the resistance mechanisms of PD1 blockade, Limagne et al. showed that accumulation of galetin-9-expressing monocytic MDSCs (mMDSCs) and TIM3-expressing CD8 T cells was found in lung cancer patients with resistance to anti-PD1 therapy, and may play a crucial role in resistance to PD1 blockade. Here, HAVCR2 is linked to lung cancer.