CD4 and neoplasm: The strongest predictive biomarkers of ex vivo resistance to CTLA-4 blockade were elevated PD-L1 expression on circulating CD4+ T cells (Fig. 3a, c, AUC = 0.79, p < 0.01, (Wilcoxon rank-sum test)) and CD8+ T cells (Fig. 3a, d, AUC = 0.76, p < 0.03 [Wilcoxon rank-sum test] without adjustment for multiple comparisons) but not on the tumor-infiltrating lymphocytes in lymph node melanoma metastases (Fig. 3b and Supplementary Fig. 6c, d).