Challenging PD-L1 expressing cytotoxic T cells as a predictor for response to immunotherapy in melanoma

We read with great interest the report by Jacquelot N et al. 1 on ‘predictors of responses to immune checkpoint blockade in advanced melanoma’. Based on an ex vivo metastatic lymph node assay (stage III, n = 37), the authors conclude that PD-L1 expression on circulating CD4 + and CD8 + T cells might be predictive biomarkers for resistance to CTLA-4 blockade. These observations were confirmed in vivo in another patient cohort, including 190 unresectable stage III and IV melanoma patients who were treated with ipilimumab.