S. ratti single infected mice responded to both, S. ratti antigen and polyclonal stimulation by CD3 engagement with IL-10 and IL-13 production whereas L. major single infected mice did not produce these Th2 cytokines (Figure 2b). The IL-10 and IL-13 production in anti-CD3 activated lymphocytes was significantly reduced in co-infected mice compared to S. ratti singly infected mice, although the

mice had been co-infected with L. major for only 2 days. S. ratti antigen-specific proliferation RAD001 was not affected by co-infection with L. major (Figure 2b). S. ratti antigen-specific IL-10 and IL-13 were reduced by trend but not significantly. Significant IFN-γ production upon anti-CD3 stimulation was observed in L. major single infected but neither in S. ratti single nor in co-infected mice although the CD3-induced proliferation was comparable in all groups. This finding suggests that the transient suppression of IFN-γ response to CD3 engagement, a typical feature of S. ratti-infected mice that we described before (10), was still present in co-infected mice at day 8 post-S. ratti infection. To analyse S. ratti and L. major-specific immune response at the same time, we chose day 16 post-S. ratti infection (i.e. day 10 post-L. major infection) and prepared the mesLN draining the site of S. ratti and the popLN draining the site of L. major infection. No antigen-specific cytokine production

was observed in the mesLN at day 16 p.i., which is in line with the declining immune response at this late stage of infection. Nevertheless, increased IL-10 and IL-13 response Napabucasin mouse to anti-CD3 stimulation were still visible in S. ratti single infected

mice and significantly suppressed in co-infected mice (Figure 2c). Also the S. ratti antigen-specific proliferation was still present in S. ratti single infected mice. L. major infection induced a slight but not significant suppression of this weaker S. ratti antigen-specific proliferation. The suppression Dynein of IFN-γ response to CD3 engagement that we observed by trend at day 8 post-S. ratti infection in co-infected mice (Figure 2b) was not present at day 16 post-S. ratti infection (Figure 2c), highlighting the transient nature of this suppression (10). Leishmania major-specific and CD3-induced proliferation and IFN-γ production, on the other hand, were not suppressed but even increased in the popLN of nematode co-infected mice while total cell numbers prepared form the popLN ex vivo were comparable (Figure 2d and data not shown). As the proliferation and IFN-γ production by unstimulated popLN were also increased in co-infected mice, the injection of S. ratti iL3 and L. major promastigotes into the same footpad apparently induced a generalized pro-inflammatory milieu. This elevated proliferation and IFN-γ production were still detectable at day 31 post-L. major infection when the footpad swelling started to decrease, indicating successful resolution of infection (Figure 2e).