SHIP1 is regulated by miR-155 in resting and monokine-stimulated human NK cells. (A) GFP⁺ NK-92 Lenti and GFP⁺ NK92 Lenti-miR-155 cells (left) and GFP⁺ NK-92 miR-Zip00 and NK-92 miR-Zip155 cells (right) were cultured in medium without IL-2 for 24 hours and then quantified for SHIP1 protein expression by Western blot. (B) Comparable NK-92 cells were then cultured in medium containing IL-12 (10 ng/mL) plus IL-18 (100 ng/mL) for 24 hours and then quantified for SHIP1 protein expression by Western blot. The relative levels of SHIP1 protein, as determined by densitometry, are indicated above the blot and expressed as densitometric units relative to the control lane (far left), which is arbitrarily set at 1.00. This experiment is representative of at least 2 such experiments performed with similar results.