NK cells in NK MACS GMP Medium (Phenol Red). NK cell fold expansion from PBMCs (n=3) using 5% AB serum and 500 IU/mL of IL-2 and 140 U/mL IL-15 during 14 days showed high fold expansion rates for both, NK MACS Medium (light purple circle) and NK MACS GMP Medium (Phenol Red) (dark purple square).