Objective: To compare the cytotoxicity of ex vivo expanded NK cells detected by flow cytometry with 3 different staining methods.
Methods: NK cells were collected from peripheral blood on the 17th day after culture. The cultured cells were divided into 3 groups: group A , B, and C. The cells in group A were stained with CFSE/Annectin-V/7-AAD; the cells in group B were stained with Annectin-V/PI, and the cells in group C cells were stained with CFSE/PI. The E:T ratios in 3 groups were 10:1, 20:1 and 40:1, respectively, the K562 cells were incubated with NK cells for 4 hrs.
Results: The purity of NK cells(CD3-CD56+) reached to (16.34±10.51)% on day 0 and to (83.63±10.63)% on the day 17 after incubation(P<0.05); the cytotoxicity of group A was significantly higher than thay of group B at different E:T ratio (P<0.05). The cytotoxicities in A, B, C groups at E:T ratio=10:1 were (36.56±3.69)%, (10.85±2.09)% and (22.35±2.71)% respectively; the cytotoxicities in A, B, C groups at E:T ratio=9:1 were (47.83±5.52)%, (39.07±5.55)% and (29.61±4.81)%; the cytotoxicities in A, B, C groups at E:T ratio=40:1 were (67.7±4.77)%, (51.51±4.43)% and (44.12±5.62)% respectively. Meanwhile, the cytotoxicity in group A was significantly higher than that in group C at different E:T ratio (P<0.05), the percentage of cytotoxicity was (36.56±3.69)% vs (10.85±2.09)%, (47.83±5.52)% vs (29.61±4.81)%, (67.7±4.77)% vs (44.12±5.62)%, respectively.
Conclusion: CFSE/Annectin-V/7-AAD is able to clearly show human NK cell cytotoxicity against human tumors. Moreover, this staining technique also allows to distinguish different stages of cytotoxic killing as early and late apoptotic phase.