Monocytic myeloid suppressor cells are involved in the exacerbated inflammation during acute Trypanosoma cruzi infection in TLR4 knockout mice.

GONZALEZ, PATRICIA ; PAROLI, AUGUSTO; GEA, SUSANA; CANO, CR

Mar del Plata

Congreso; Meeting SAI, SAIC, SAFE; 2016

SAI, SAIC, SAFE

Background: Myeloid-derived suppressor cells (MDSCs) are key players in the resolution of hepatic inflammation during acute T. cruzi infection. There are two subsets: granulocytic (G-MDSCs: CD11b+LY6G+LY6Clow) and monocytic (M-MDSCs: CD11b+LY6G−LY6Chigh). MDSCs may suppress immune response through reactive oxygen species (ROS) and nitric oxide (NO) production. Recognition by toll-like receptors (TLRs) is critical for defense against T. cruzi and for triggering hepatic pathology. Previously, we reported that TLR4 deficiency produces an increase in hepatic M-MDSCs and ROS-producing M-MDSCs associated with high levels of GPT in plasma. Here, we evaluated plasma cytokine levels, hepatic intracellular IL10+, NO+, CCR5+ or CXCR2+ G or M-MDSCs in TLR2 and TLR4 deficient and WT mice. Methods: Male C57BL/6 WT, TLR2-/- and TLR4-/- mice were i.p. infected with 1000 trypomastigotes (Tulahuén strain). MDSCs phenotype, intracellular IL10, CCR5 and CXCR2 expression, and NO detection were analyzed in G- or M-MDSCs from intrahepatic leukocytes by flow cytometry at 19 days post infection. Plasma cytokine levels (TNF-á, IL6, IL12, IFN-ã and IL10) were quantified by ELISA. Results: During infection, TLR4KO mice presented a higher number of NO producing hepatic M-MDSCs and lower number of NO producing G-MDSCs than WT and TLR2KO. TLR4KO mice showed a strong increase of inflammatory cytokines vs. other groups while IL10 remained similar to uninfected control. Likewise, intracellular IL10 expression did not change in any MDSCs population. The infection induced an increase in CCR5 expressing hepatic M-MDSCs from TLR4KO and WT mice while the number of CXCR2 expressing G-MDSCs was similar between both groups. Conclusion: The absence of TLR4 during acute infection triggered an increase in NO producing hepatic M-MDSCs as well as in plasma inflammatory cytokines without changes in IL10 levels, suggesting that the lack of TLR4 would be involved in the exacerbated inflammation of the liver.