SELL and neoplasm: Since the IFP+ T cells do produce more IL-2 ex vivo, have an increased frequency of cells with central memory characteristics (CD62L expression, low PD-1) and preferentially persist in tumors, these results suggest the improved tumor control observed in tumor-bearing mice may be largely due to increased persistence of tumor-specific T cells with enhanced proliferative capacity rather than enhanced cytolytic function of individual cells.