A comparative analysis of cytokine responses, cell surface marker expression and MAPKs in DCs matured with LPS compared with a panel of TLR ligands.

Dendritic cells (DCs) are professional antigen-presenting cells that play a vital role in shaping adaptive immunity. DC maturation begins when exogenous danger signals bind to the appropriate toll-like receptor (TLR) and initiate expression of cell surface markers and the secretion of cytokines. This process occurs through defined mitogen-activated protein kinase (MAPK) signalling pathways. Of the 13 known mammalian TLRs, lipopolysaccharide (LPS), which activates TLR4, is the most commonly used ligand for the maturation of DCs in vitro. This comprehensive study measures cytokine secretion and cell surface marker expression in murine bone-marrow-derived DCs following maturation with LPS compared to DCs matured with a panel of other TLR-ligands (zymosan A (TLR2/6), PGN (TLR2), poly(I:C) (TLR3), flagellin (TLR5) and CpG-ODN1826 (TLR9)). The role of MAPK signalling pathways in the maturation process was also examined. Results demonstrate that zymosan A and CpG induce comparable cytokine and cell surface marker profiles to LPS. The remaining ligands differed significantly for cytokine and CD40 expression, but not for CD80 and CD86 expression. While there were differences for MAPK signalling pathways for all ligands, the effect of the inhibitors were broadly similar. These findings broaden our knowledge of TLR ligand-matured DCs.