Discrimination between NK and LAK cytotoxic activities of murine spleen cells by MTT assay: differential inhibition by PGE(2) and EDTA.

In the present study we propose a mathematical approach to improve the analysis of NK and LAK activities measured by MTT assay adapted for murine cells. We found that to calculate NK activity, high E:T ratios should be used (up to 50:1) and the phenomenon fits to a linear least-squares analysis. However, 5-fold less effector cells (10:1, E:T) should be used to detect LAK activity and the phenomenon has a nonlinear exponential behavior. Using this approach, we showed that EDTA inhibits LAK but not NK activity whereas PGE(2) inhibits NK but not LAK activity. In conclusion, this analytical approach allowed the discrimination between NK and LAK activities and exposed differences between these two cytotoxic activities.