CTSS and influenza: At least for IKDCs we favour the latter explanation as we did not find real evidence of direct infection of IKDCs by influenza (low levels of viral nucleoprotein staining compared with cDCs [13], [21]), and as IKDCs highly expressed members of the ER retro translocation machinery Sec61a1 (involved in cross-presentation) and cathepsin S, also recently implicated to play a role in crosspriming [28], [29].