Both Conventional and Interferon Killer Dendritic Cells Have Antigen-Presenting Capacity during Influenza Virus Infection

Natural killer cells are innate effector cells known for their potential to produce interferon-γ and kill tumour and virus-infected cells. Recently, B220+CD11cintNK1.1+ NK cells were found to also have antigen-presenting capacity like dendritic cells (DC), hence their name interferon-producing killer DC (IKDC). Shortly after discovery, it has already been questioned if IKDC really represent a separate subset of NK cells or merely represent a state of activation. Despite similarities with DCs, in vivo evidence that they behave as bona fide APCs is lacking. Here, using a model of influenza infection, we found recruitment of both conventional B220− NK cells and IKDCs to the lung. To study antigen-presenting capacity of NK cell subsets and compare it to cDCs, all cell subsets were sorted from lungs of infected mice and co-cultured ex vivo with antigen specific T cells. Both IKDCs and conventional NK cells as well as cDCs presented virus-encoded antigen to CD8 T cells, whereas only cDCs presented to CD4 T cells. The absence of CD4 responses was predominantly due to a deficiency in MHCII processing, as preprocessed peptide antigen was presented equally well by cDCs and IKDCs. In vivo, the depletion of NK1.1-positive NK cells and IKDCs reduced the expansion of viral nucleoprotein-specific CD8 T cells in the lung and spleen, but did finally not affect viral clearance from the lung. In conclusion, we found evidence for APC function of lung NK cells during influenza infection, but this is a feature not exclusive to the IKDC subset

Human plasmacytoid dendritic cells are equipped with antigen-presenting and tumoricidal capacities

Item does not contain fulltextHuman plasmacytoid dendritic cells (pDCs) represent a highly specialized naturally occurring dendritic-cell subset and are the main producers of type I interferons (IFNs) in response to viral infections. We show that human pDCs activated by the preventive vaccine FSME specifically up-regulate CD56 on their surface, a marker that was thought to be specific for NK cells and associated with cytolytic effector functions. We observed that FSME-activated pDCs specifically lysed NK target cells and expressed cytotoxic molecules, such as tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and granzyme B. Elevated levels of these molecules coincided with the expression of CD56, indicative for skewing human pDCs toward an interferon-producing killer DC subset. Detailed phenotypical and functional analysis revealed that pDCs attained a mature phenotype, secreted proinflammatory cytokines, and had the capacity to present antigens and stimulate T cells. Here, we report on the generation of CD56(+) human interferon producing killer pDCs with the capacity to present antigens. These findings aid in deciphering the role for pDCs in antitumor immunity and present a promising prospect of developing antitumor therapy using pDCs