Therefore, peritoneal selleck screening library Mφs from naive or T. cruzi-infected mice were co-cultured with naive CD90.2+ T cells purified from spleens of BALB/c mice. Antibodies specific for PD-1/PD-Ls were added to the co-cultures for 72 hr and proliferation was determined before the addition of [3H]thymidine. F4/80+ Mφs from naive mice favour Con A-stimulated naive mouse T-cell proliferation. However, F4/80+ Mφs from T. cruzi-infected mice suppress naive CD90.2+ T-cell proliferation (Fig. 2) as was shown

previously.54 T-cell proliferation was restored when anti-PD-1 or anti-PD-L1 antibodies were added. Nevertheless, PD-L2 blocking antibody treatment did not re-establish T-cell proliferation. These data suggest that T. cruzi induces a suppressive phenotype of Mφs through the up-regulation of PD-L1, which inhibits activated CD90.2+ T cells. Several studies have shown that Arg I-mediated depletion of l-arginine leads to T-cell suppression.26,27 To discover

whether Arg I is involved in the immunosuppression observed in Fig. 2, we determined Arg I expression and activity in peritoneal cells treated with PD1 and PD-L blocking antibodies and infected in vitro with T. cruzi. Arg I expression and activity were up-regulated in infected cells compared with uninfected cells. Interestingly, Arg I expression and activity were enhanced in infected cells treated with anti-PD-L2 blocking antibody compared with infected cells. However, anti-PD-1 and anti-PD-L1 blocking Hydroxychloroquine antibodies did not modify Arg I in infected cells (Fig. 3a,b). Therefore, the increase in Arg I activity and expression observed in anti-PD-L2-treated RG7420 supplier cells might explain why anti-PD-L2 blocking antibody was not able to re-establish T-cell proliferation

(Fig. 2). Because l-arginine is the substrate for Arg I as well as for iNOS, we evaluated iNOS expression and NO production in peritoneal cells from infected mice or cells infected in vitro treated with blocking antibodies. Peritoneal cells from infected mice produce large amounts of NO compared with uninfected cells (Fig. 4a). In addition, the same effect was observed in peritoneal cells infected in vitro (Fig. 4c). Anti-PD-L2 blocking antibody treatment reduced NO production and iNOS expression in cells from infected mice (Fig. 4a,b) as well as in cells infected in vitro (Fig. 4c,d). On the other hand, we observed a slight increment in NO production in cells from infected mice treated with anti-PD-1 or anti-PD-L1. Therefore, anti-PD-L2 blocking antibody shifts the Arg I/iNOS balance towards Arg I in T. cruzi-infected cells (Figs 3 and 4). It has been demonstrated that T2-type cytokines shift l-arginine metabolism in Mφs towards Arg I, leading to polyamine biosynthesis. To investigate the influence of the PD-1/PD-Ls pathway in the cytokine profile, IL-10 and IFN-γ production were determined in infected cells treated with PD-1/PD-Ls blocking antibodies.