A critical DC-produced factor for polarizing Th1 immunity is the heterodimeric cytokine IL-12. Although IL-12 production can be triggered by stimulation of DC with single Toll-like receptor (TLR) ligands, optimized production requires that multiple signals be delivered to the DC. These include dual TLR ligands, single TLR ligands paired with the cytokine interferon-gamma or CD40L combined with these other signals. Although calcium mobilizing signals have been shown to induce phenotypical maturation of DCs, they have never been shown to synergize with TLR or cytokine signals to enhance IL-12 production. Murine bone marrow-derived DCs pretreated with calcium ionophore 4 hours prior to TLR ligand exposure significantly enhance IL-12 p70 production by DCs. Thapsigargin, a compound that enhances intracellular calcium levels by a different mechanism, had similar effects. The drugs cyclosporine A and ascomycin, which antagonize the activity of the calcium-dependent serine-threonine phosphatase, calcineurin, suppressed the IL-12-enhancing activity of calcium mobilization. When mouse T cells were co-cultured with allogeneic DCs activated with calcium ionophore, TLR ligands, or both, paired activation stimulation induced DCs with superior T cell stimulatory capacity as measured by IFN-gamma output (ELISA), and proliferation measured by CFSE dilution. Calcium mobilization may therefore provide a method for superior activation of Th1-polarizing DCs for clinical testing.
- Copyright © 2013 by The American Association of Immunologists, Inc.