A dysfunctional subset of T cells specific to lung tumors is resistant to immune checkpoint blockade (ICB) therapy. MIT scientists show in studies on mouse models of lung cancer that T-cell exhaustion is not the cause of this T-cell dysfunction as nonresponsive T cells are found even before they reach the tumor. Treatment with IL-2 and IL-12 restores regular function in these cells, and along with ICB reduces tumor size in mice.