Effects of the metabolite fraction MTB and cell wall fraction CW on NK cell activation status and cytotoxic activity was evaluated using human PBMC. (A) Both MTB and CW fractions induced the expression of the activation marker CD69 on CD3 negative, CD56 positive NK cells in a dose-dependent manner. The effect was statistically significant for the 1:400 dilution of both MTB and CW. (B) Expression of CD107a on NK cells pretreated with MTB or CW showed a mild increase over baseline. The graphs show the averages and standard deviations of each culture condition performed in triplicate. The data shown are representative of three experiments performed on cells from different donors.