PD-L2 negatively regulates Th1-mediated immunopathology during Fasciola hepatica infection

STEMPIN, CC; MOTRAN, CC; AOKI, MP; FALCON CR; CERBAN, FM; CERVI L

Oncotarget

Impact Journal

Lugar: En revisión; Año: 2016 vol. 7 p. 77721 - 77731

Macrophage plasticity is critical for controlling inflammation including thoseproduced by helminth infections, where alternatively activated macrophages (AAM)are accumulated in tissues. AAM expressing the co-inhibitory molecule programmeddeath ligand 2 (PD-L2), which is capable of binding programmed death 1 (PD-1) expressed on activated T cells, have been demonstrated in different parasiticinfections. However, the role of PD-L2 during F. hepatica infection has not yet been explored. We observed that F. hepatica infection or a F. hepatica total extract (TE) injection increased the expression of PD-L2 on peritoneal macrophages. In addition,the absence of PD-L2 expression correlated with an increase in susceptibility to F.hepatica infection, as evidenced by the shorter survival and increased liver damage observed in PD-L2 deficient (KO) mice. We assessed the contribution of the PD-L2 pathway to Th2 polarization during this infection, and found that the absence of PD-L2 caused a diminished Th2 type cytokine production by TE stimulated splenocytes from PD-L2 KO infected compared with WT mice. Besides, splenocytes and intrahepatic leukocytes from infected PD-L2 KO mice showed higher levels of IFN-γ than those from WT mice. Arginase expression and activity and IL-10 production were reducedin macrophages from PD-L2 KO mice compared to those from WT mice, revealing a strong correlation between PD-L2 expression and AAM polarization. Taken together,our data indicate that PD-L2 expression in macrophages is critical for AAM induction and the maintenance of an optimal balance between the Th1- and Th2-type immune responses to assure host survival during F. hepatica infection.