Following influenza A computer virus (IAV) contamination, development of a robust IAV-specific CD8 T cell response is required for clearance of main contamination and enhances memory protection. pDC must utilize the direct presentation pathway for this rescue. This failure of pDC from 142t-IAV donors to rescue the IAV-specific CD8 T cell response is not due to differences in the overall ability of 142t-IAV to replicate within Afatinib kinase inhibitor the lungs or generate defective viral genomes or to differences in levels of costimulatory molecules required for this conversation. We further demonstrate that bypassing the antigen presentation pathway by covering the 142t-IAV pDC with IAV peptide epitopes restores their ability to rescue the IAV-specific CD8 T cell response. IMPORTANCE IAV continues to be a global health burden, infecting 5 to 20% of the global populace annually. Continued investigation into the mechanisms that mediate protective immune responses against IAV is usually important to improving current vaccination and antiviral strategies antagonistic toward IAV. Our findings offered herein demonstrate a key requirement for pDC promotion of effector CD8 T cell survival: that rather than utilizing cross-presentation, pDC must be infected and utilize the endogenous pathway for presentation of antigens to CD8 T cells during IAV infections. This suggests that targeting presentation via the endogenous pathway in pDC could be important for the development of unique antiviral cellular therapies. INTRODUCTION The development of a cytotoxic CD8 T cell response is usually key in clearance of influenza A computer virus (IAV) contamination. Following activation of naive CD8 T cells in the lung-draining lymph nodes (dLNs), our studies have exhibited that effector CD8 T cells must interact with either plasmacytoid DC (pDC) or CD8+ DC within the lungs in order to avoid apoptosis, generate a full-magnitude CD8 T cell response, and lead to clearance of computer virus from the host (1, 2). The rescue of the T cells from death by DC during this pulmonary DC-CD8 T cell conversation requires presentation of viral antigen in the context of major histocompatibility complex class I (MHC-I), contamination, IAV replicates in both lung epithelial cells and antigen-presenting cells (APCs) (4,C7). DC are positioned in the airways and interstitium of the lungs and acquire viral antigens from surrounding dying epithelial cells or through direct contamination. DC then process this antigen and express viral peptide-containing MHC-I molecules, which are utilized in the initial activation of naive CD8 T cells in the dLN and for maintaining the CD8 T cells within the lung. The viral peptides or proteins acquired from IAV-infected, dying epithelial cells and during direct contamination of the DC are processed and offered via 2 pathways: cross-presentation and the endogenous pathway, respectively Afatinib kinase inhibitor (examined in reference 8). While CD8+ DC are well documented to be effective cross-presenters of antigens, pDC are typically not regarded as efficient cross-presenters (9, Afatinib kinase inhibitor 10). Interestingly, however, pDC have been demonstrated to cross-present antigens following Toll-like receptor 7 (TLR7) activation (11) and produce type S1PR4 I interferon (IFN) following TLR7 activation during IAV contamination (12). Therefore, it is possible that pDC could utilize the cross-presentation pathway to present viral antigens to CD8 T cells in the lungs during IAV contamination. At this time, whether Afatinib kinase inhibitor pDC can cross-present antigens during an IAV contamination remains controversial (6, 13). While a pDC cell collection has been demonstrated to cross-present viral antigens after exposure to IAV (13), exposure of human main pDC to IAV has been reported to impair their ability to cross-present antigens to CD8 T cells (6). As antigen presentation by either pDC or CD8+ DC to effector CD8 T cells is required within the lungs during IAV contamination, the possibility that these DC subsets could utilize unique pathways of antigen processing or presentation in order to maintain the pulmonary IAV-specific CD8 T cell response is usually intriguing. Afatinib kinase inhibitor The utilization of disparate pathways by pDC and CD8+ DC subsets to process and present antigen during their normal rescue of the IAV-specific CD8 T cell response from apoptosis in the lungs during IAV contamination (2) would be the first distinction between these two DC subsets in their requirements for acquiring the ability to protect CD8 T cells from apoptosis and drive strong T cell immunity in the lungs. Knowledge of such potential distinctions would aid in further delineating the pathways.