Fig. 3

Neutralization of CCL2 diminishes the MSC-mediated stimulation of NK cells. a, b NK cells were incubated alone or in co-culture with MSCs in the presence of neutralizing antibodies against CCL2 or isotype control antibodies for 24 h. Thereafter, the cells were stimulated with IL-12 and IL-18 for 24 h and the concentration of IFN-γ in the supernatants was determined. b Freshly isolated NK cells were incubated with conditioned media (CM) from NK cells, MSCs, MSC/NK cell co-cultures, and cell-free medium each in the presence of neutralizing antibodies against CCL2 or the isotype control. Thereafter, all cells were stimulated with IL-12 and IL-18 for 24 h. The amount of IFN-γ in the supernatant was quantified. a, c Bar graphs showing mean ± SD of 4–5 replicates of one representative experiment. Statistical analysis was performed using one-way ANOVA followed by Bonferroni multiple comparison test. b, d Cumulative and normalized data of eight independent experiments. One hundred percent was equivalent to median (interquartile range) 132 (70–340) pg/ml and 87 (38–308) pg/ml in (b) and (d), respectively. Statistical analysis was performed using the Wilcoxon signed-rank test. *p < 0.05**p < 0.01***p < 0.001. MSC mesenchymal stromal/stem cell, NK natural killer, CCL2 C-C ligand 2, IFN interferon