Nature Reviews Cancer 15, 409–425 (2015)

In the version of this article that was originally published, there was an error in Figure 1 on page 410 and in Figure 4 on page 417. In both figures, programmed cell death protein 1 (PD1) was shown to be expressed on the cancer cell and PD1 ligand 1 (PDL1) was shown to be expressed on T cells, whereas PD1 should be expressed on T cells and PDL1 on cancer cells. These errors have now been corrected in the online versions of the article.