Finally, the participation of the adaptor protein MyD88 downstream of TLRs in the induction of IFN-I was ruled out, as its absence in MyD88 knock-out macrophages did not affect the increased gene expression of IFN-β (Figure 3C) or of IFN-α (Figure 3D) upon infection with L. donovani. This is in line with the current knowledge that IFN-related responses downstream of TLRs occur mainly via the TRIFF adaptor protein (18). Here, IFNB1 is linked to infection.