Immunostaining for IL-2 in transduced but nonselected NK-92 cells. (A) P-NK-92 cells incubated for 48 hours in the absence of exogenous IL-2 prior to staining. (B) Transduced nonselected (48 hours posttransduction) IL-2/Neo/NK-92 cells incubated for 48 hours in the absence of exogenous IL-2 prior to staining. Insert shows an IL-2–expressing NK cell (original magnification ×1,000). The staining reaction was developed with AEC, and the cells were counterstained with hematoxylin. For A and B, original magnification is ×500.