LAG3 and cancer: We chose to focus on these coinhibitory receptors because (a) they were both differentially expressed between Tr1 and Th1 cells (Figure 1C), (b) LAG3 has a strong association with Tr1 cells and their functions (14), and (c) TIM3 loss-of-function mutations are associated with human diseases and it has emerged as an important target for immune checkpoint blockade in trials to treat several different human cancers (28).