[Leishmania mexicana DNA activates murine macrophages and increases their TLR9 expression]

Macrophages are immune system cells that recognize pathogen associated molecular patterns (PAMPs) through receptors that can be located on the cell membrane or in intracellular compartments, such as the TLR (toll like receptors). Different TLRs bind to ligands shared among multiple pathogens. The binding of ligands to TLRs induces a signaling cascade that leads to cytokine and co-stimulatory molecule production due to the nuclear translocation of NF-kappaB. We demonstrated that Leishmania lipophosphoglycan (LPG) is a ligand for TLR2, leading to NK-cell activation. Schieicher et al. recently reported that genomic DNA from Leishmania infantum activates plasmacitoid dendritic cells through TLR9, leading to IFN type I production.

In the present study we explored wether Leishmania mexicana DNA contained non-methylated CpG motifs able to activate murine bone marrow derived macrophages, as previously described for bacterial DNA containing CpG motifs.

We observed that Leishmania mexicana DNA contains non-methylated CpG morifs able ofactivating murine bone marrow derived macrophages, leading to the production of proinflammatory cytokines such as TNFalpha and IL- 12(P40) as well as the over expression of mRNA for TLR9.