Methods for identifying cancer patients amenable to anti-cancer immunotherapy are provided along with methods of monitoring cancer therapy. Also provided are methods of treating cancer patients amenable to anti-cancer immunotherapy. The methods involve determining the level of CD127<;low>;PD-1<;low>;T cells. The patients are treated with an immune checkpoint inhibitor, such as an anti-CTLA-4 antibody, e.g. ipilimumab.