Our optimized in vitro set-up revealed multiple distinct functional clusters of TILs expressing heterogeneous activation markers and functions on a protein level, a finding supported by recent data demonstrating that most tumor-specific TILs expanded from renal cell carcinoma express CD137, but may lack significant expression of common effector molecules (47). The gene discussed is TNFRSF9; the disease is hereditary clear cell renal cell carcinoma.