Aim: To investigate the effect of the TLR ligand (R-848) and IL-12 on the production of IFN-gamma by human NK cell subsets.
Methods: PBMC or purified NK cells were isolated from normal human peripheral blood and cultured with R-848, IL-12 , R-848+ IL-12. The level of IFN-gamma in the culture supernatants was measured by ELISA. The cell subsets which produced IFN-gamma were detected and analyzed by flow cytometry(FCM).
Results: PBMC cultured with different concentrations of TLR ligands (R-848, LPS and CpG) could induce IFN-gamma production in a dose dependent manner. Among these three TLR ligands, R-848 was the best one in induction of IFN-gamma production by PBMC. FCM analysis indicated that R-848 could induce IFN-gamma expression by CD56(+) cells, but not CD4(+) or CD8(+) T cells. Similarly, IL-12 could stimulate NK cells to produce IFN-gamma. In addition, R-848 and IL-12 had synergistic effect on the production of IFN-gamma by PBMC and purified NK cells including CD56(bright) and CD56(dim) subsets.
Conclusion: Engagement of TLR7/8 by R-848 stimulation with IL-12 could induce IFN-gamma production by CD56(bright) NK cells which indicated that TLRs and cytokines played an important role in the regulation of biologic function of NK cells.