CD4 and melanoma: Here we develop a new type of dynamic biomarker for anti-PD-1 immunotherapy, which is based on the interferon gamma (IFN-γ) cytokine secretion kinetics of circulating lymphocytes in the peripheral blood, to reflect evolving immune functions and further predict individual responsiveness to checkpoint immunotherapies.20,21 Specifically, the secretory kinetics of IFN-γ, rather than concentration measurements at a single time point, are evaluated in peripheral CD4+ and CD8+ T cells from melanoma-bearing mice during the treatment of anti-PD-1 immunotherapy.