Proteomic and single-cell transcriptomic dissection of human plasmacytoid dendritic cell response to influenza virus

Plasmacytoid dendritic cells (pDCs) represent a rare innate immune subset uniquely endowed with the capacity to produce substantial amounts of type-I interferons (IFN-I). This function of pDCs is critical for effective antiviral defenses and has been implicated in autoimmunity. While IFN-I and select cytokines have been recognized as pDC secreted products, a comprehensive agnostic profiling of the pDC secretome in response to a physiologic stimulus has not been reported. We applied LC-MS/MS to catalogue the repertoire of proteins secreted by pDCs in response to challenge with live influenza H1N1. Additionally, using single-cell RNA-seq [scRNA-seq], we perform multidimensional analyses of pDC transcriptional diversification following stimulation. Our data reveal an abundance of protein species released by pDCs in addition to IFN-I, and evidence highly specialized roles within the pDC population ranging from dedicated cytokine super-producers to cells with APC-like functions. Moreover, dynamic expression of transcription factors and surface markers characterize activated pDC fates. pDCs were stimulated with flu virus and examined at 0, 6 and 24 hours to see their temporal response