The allantoic fluid was harvested after 2 d. and CD8 T cells. When lung CD11chi DCs and macrophages or langerin+CD11b?CD11chi DCs were depleted using either CD11cCdiphtheria toxin receptor (DTR) or langerin-DTR mice, CKD-519 the development of virus-specific CD8+ T cells was severely delayed, which correlated with CKD-519 increased clinical severity and a delayed viral clearance. 120G8+ CD11cint pDCs also accumulated in the lung and LNs carrying viral NP, but CKD-519 in their absence, there was no effect on viral clearance or clinical severity. Rather, in pDC-depleted mice, there was a reduction in antiviral antibody production after lung clearance of the computer virus. This suggests that multiple DCs are endowed with different tasks in mediating protection against influenza computer virus. Influenza type A is usually a cytolytic computer virus that causes acute respiratory contamination, of which the clinical outcome can vary greatly. The way in which the innate and adaptive immune systems initially recognize and deal with replicating computer virus could CKD-519 be decisive in determining the outcome of contamination, as this might heavily influence the kinetics of viral clearance (1C3). Little is known about the initial recognition event of influenza computer virus by the lung immune system in vivoIFN- was produced in the lungs after X-31 contamination, but levels were not affected by CD11chi cell depletion (Fig. 4 F). The data in this paragraph show that lung CD11chi cells are required for an efficient immune response against influenza computer virus contamination. However, as CD11c is also highly expressed by alveolar macrophages and these cells are also depleted by local i.t. administration of DT, we performed adoptive transfer reconstitution experiments (19, 37). Tg mice depleted of CD11chi cells therefore received i.t. unpulsed wild-type CD11chi DCs or alveolar macrophages at the moment of contamination. DCs were capable of restoring the CTL response (Fig. 4 G), and as a consequence, viral clearance from the lung was complete by day 8 (Fig. 4 G, right). Alveolar macrophages were not capable of restoring antiviral immunity or viral clearance. These experiments demonstrated that CD11chi DCs are sufficient for inducing an adequate immune response against influenza computer virus contamination. Depletion of lung langerin+ DCs aggravates contamination parameters The conditional depletion of CD11chi cells in CD11c-DTR mice did not allow us to address the contribution of tracheal CD11b?CD11chi DCs, as neither tracheal CD11b-CD11chi DCs nor their CD11b? progeny in the MLNs were depleted in CD11c-DTR mice. Therefore, we performed experiments in langerin-DTR mice. When DT was administered i.t. to these mice, there was a strong reduction in CD11b?CD11chi DCs in the trachea, whereas tracheal CD11b+ DCs were unaffected. In the lungs, CD11chi DCs were depleted, whereas alveolar macrophages were unaffected. The CD8+CD11b? resident MLN cDC subset does not express langerin, and consequently, lung administration of DT to these mice only led to a reduction in lung-derived CD11b?CD8? migratory PPP1R60 DCs (Fig. S3). Depletion of langerin+ DCs resulted in a severe weight loss in the mice until 8 dpi (Fig. 5 B), and this was correlated with a significant decrease in CTL response (Fig. 5 C) and a deficient viral clearance at 8 dpi (Fig. 5 D). Open in a separate window Physique 5. Effect of conditional depletion of langerin+ DCs cells during influenza contamination. Langerin-DTR Tg mice received an i.t. injection of DT on day ?1, followed by X-31 i.n. contamination. (A) Efficient depletion of MHCII+CD11c DCs in lung after DT treatment. Numbers indicate percentages of live cells within the gate. (B) Body weight after influenza contamination. A weight loss of 20% represents a sublethal contamination. (C) Virus-specific CTL response in spleen and lung measured by Flupeptide/H-2Db tetramer (TM) staining. (D) Viral titers measured in lung tissue after influenza X-31 contamination. Computer virus is normally cleared completely at 8 dpi. The values are representative of five mice per group and are expressed as mean SEM. Comparable results were obtained from at least two individual experiments. *, P 0.05; **, P 0.01. nd, nondetectable. Depletion of pDCs did not alter the course of contamination The experiments using CD11c-DTR and langerin-DTR mice mainly depleted CD11chi cells, whereas CD11cint pDCs are globally not affected by this targeting strategy (43). To additionally address the role of pDCs, we CKD-519 performed experiments in which pDCs were depleted by injection of the 120G8 mAb (22). Using.