Figure 8. Cis-Delta-Like 1 expression on NK cells limits Notch signaling and acquisition of KIR.
(A) A two-step magnetic enrichment was used to obtain CD56+CD3− KIR+ or KIR− NK cells and delta-like 1 (DLL1/top) and delta-like 4 (DLL4/bottom) transcripts were assessed and normalized to 18s (n = 6). (B) DLL1 (top) and DLL4 (bottom) protein expression was assessed (in terms of MFI) on CD56dimCD3− NK cells from PBMCs of healthy human donors (n = 4). (C) DLL1 transcript (normalized to GAPDH) and (D) protein (in terms of MFI) expression were analyzed from CD56bright, CD56dimKIR− and CD56dimKIR+ NK cells sorted from PBMCs (n = 4). (E) CD56bright NK cells were sorted from PBMCs and treated for 0 hrs (no treatment) or 72 hrs with 10 ng/ml IL-15. Cells were then harvested and assessed for DLL1 transcript expression and normalized to GAPDH (n = 4). (F) d28 CD34 derived NK cells were harvested and transduced with siRNA controls (siC) or siRNAs specific for DLL1 (siDLL1) and then rested for one day. Cells were next cultured for 6 days with 10 ng/ml IL-15 and OP9-DLL1 cells to provide notch signals in trans and harvested at day 35. KIR expression was then assessed on the CD56+CD3− NK cells (n = 4).