AHR expression in IL-21–expanded NK cells. (A) RNA-seq data showing the expression of aryl hydrocarbon receptor (AHR), aryl hydrocarbon receptor repressor (AHRR), and cytochrome P450 isoform B1 (CYP1B1) from naïve (resting) and day 14 expanded NK cells. NK cells isolated from healthy donors were expanded for a period of 2 weeks with irradiated K562 feeder cells overexpressing membrane bound IL-21 and 4-IBBL (FC21) in RPMI media containing IL-2 (50 IU/mL). (B) Immunoblot showing the expression of AHR from FC21 expanded NK cells at the indicated time points. Protein lysates prepared from NK cells were probed with anti-AHR or anti-actin antibodies. (C-D) Quantitative real-time PCR showing the expression of AHR targets genes CYP1B1 and AHRR from NK cells expanded with DMSO (control) or 1 μm Stemregenin (SR-1) on day 7 (D7) and day 14 (D14). The value on the y axis represents fold change in gene expression relative to the D7 control NK cells.