NK cells express PU.1.

Cell lysates were generated from thymocytes, splenocytes, pre-B cells (cell line 18.81), and purified splenic IL-2–activated NK cells. Protein extracts were resolved by SDS-PAGE and probed by Western blotting with an affinity-purified anti-PU.1 antibody. Blots were stripped and reprobed with antitubulin antibody to control for sample loading.