Gambichler T, et al. - Since T-regulatory lymphocytes (Tregs) upregulation is known as one of the various immune escape mechanisms of malignancies, researchers investigated how circulating Tregs subpopulations in patients with stage III melanoma are influenced by adjuvant nivolumab during the start of treatment. They found that after the initiation of adjuvant treatment with the PD-1 blocking antibody nivolumab, there was a quick and continuous decrease in circulating PD-1⁺Tregs. This drop was paralleled with a rise of CTLA-4+Tregs. Findings are suggestive of a possible role of the expression of PD-1 and CTLA-4 on Tregs as a possible biomarker for the effectiveness of immune checkpoint blockade in melanoma.