CD4 and neoplasm: We took advantage of this tumor model, since it is characterized by (a) a high level of T‐cell infiltration [13], (b) the presence of PD‐1pos CD8+ (but largely not CD4+) TILs (Fig. S1A), (c) the expression of PD‐1 ligand PD‐L1 (but not PD‐L2) in tumor cells (Fig. S1B), and (d) the expression of PD‐L1 and PD‐L2 in ca. 10% and 2% of tumor‐infiltrating CD45pos non‐T (i.e., CD4neg CD8neg) cells (Fig. S1C).