PDCD1 and cancer: Using a conditional allele that allowed myeloid-specific (PD1f/fLysMcre) or T cell-specific (PD1f/fCD4cre) targeting of the Pdcd1 gene, Strauss and colleagues could recently show that granulocyte/macrophage progenitors (GMPs), which accumulate during cancer-driven emergency myelopoiesis and give rise to MDSCs, express PD1 which is of high therapeutic relevance.