CD28 and neoplasm: Whereas naïve lung and blood mostly contained differentiated NK cells, metastatic lungs harbored a large cluster of tumor-associated NK cells (Tumor NK) expressing markers of less differentiated NK cells (Emb, Cd27, Ccr2, Cd28, Thy1 or Sell) (Fig. 4H–J and Fig. S5A, B), confirming our flow cytometric data (Fig. 4E, F).