Exposure to 6MP decreases activity of Rac1 but not RhoA or Cdc42. (A) Rac 1 activity measured by immunoassay kit in surviving NK cells following culture with 5 μM 6-MP or 100 μM ITX3 (a known inhibitor of guanine nucleotide exchange factor), at 24 h ANOVA [F(2,6) = 27.9, p = 0.0009] and at 72 h ANOVA [F(2,9) = 19.6, p = 0.0005]. OD = Optical density (B) Western blot showing loading control (beta-actin) and Rac1 in NK cells isolated from 2 healthy individuals following 24 h of culture. Densitometry analysis does not show differences in ratio of Rac 1 to beta-actin between cells exposed and unexposed to 6MP (Student’s t-test, two tailed. p = 0.32).(C) RhoA and Cdc42 activity measured using an immunoassay kit following 24 h of culture with 6-MP.