Modulation of respiratory dendritic cells during Klebsiella pneumonia infection

Holger Hackstein,Nelli Baal,Achim D Gruber,Gabriela Michel,Jürgen Lohmeyer,Gregor Bein,Olivia Kershaw,Susanne Herold,Sabine Kranz,Andreas Wachtendorf,Anne Lippitsch

doi:10.1186/1465-9921-14-91

Abstract

BackgroundKlebsiella pneumoniae is a leading cause of severe hospital-acquired respiratory tract infections and death but little is known regarding the modulation of respiratory dendritic cell (DC) subsets. Plasmacytoid DC (pDC) are specialized type 1 interferon producing cells and considered to be classical mediators of antiviral immunity.MethodBy using multiparameter flow cytometry analysis we have analysed the modulation of respiratory DC subsets after intratracheal Klebsiella pneumonia infection.ResultsData indicate that pDCs and MoDC were markedly elevated in the post acute pneumonia phase when compared to mock-infected controls. Analysis of draining mediastinal lymph nodes revealed a rapid increase of activated CD103+ DC, CD11b+ DC and MoDC within 48 h post infection. Lung pDC identification during bacterial pneumonia was confirmed by extended phenotyping for 120G8, mPDCA-1 and Siglec-H expression and by demonstration of high Interferon-alpha producing capacity after cell sorting. Cytokine expression analysis of ex vivo-sorted respiratory DC subpopulations from infected animals revealed elevated Interferon-alpha in pDC, elevated IFN-gamma, IL-4 and IL-13 in CD103+ DC and IL-19 and IL-12p35 in CD11b+ DC subsets in comparison to CD11c+ MHC-class IIlow cells indicating distinct functional roles. Antigen-specific naive CD4+ T cell stimulatory capacity of purified respiratory DC subsets was analysed in a model system with purified ovalbumin T cell receptor transgenic naive CD4+ responder T cells and respiratory DC subsets, pulsed with ovalbumin and matured with Klebsiella pneumoniae lysate. CD103+ DC and CD11b+ DC subsets represented the most potent naive CD4+ T helper cell activators.ConclusionThese results provide novel insight into the activation of respiratory DC subsets during Klebsiella pneumonia infection. The detection of increased respiratory pDC numbers in bacterial pneumonia may indicate possible novel pDC functions with respect to lung repair and regeneration.

Highlights

Klebsiella spp. are gram-negative bacteria and important opportunistic pathogens causing life-threatening nosocomial infections [1,2]
Total dendritic cell (DC) were further dissected by flow cytometry into four major subsets, MoDC, CD11b+ DC, CD103+ DC and Plasmacytoid DC (pDC) and relative DC subset frequencies and absolute DC subset numbers were calculated (Figure 1B,C; Figure 2)
After infection (48 h p.i.), relative CD103+ DC numbers were significantly decreased in accordance with their reported function to rapidly transport antigen to regional lymph nodes [34]

Summary

Introduction

Klebsiella spp. are gram-negative bacteria and important opportunistic pathogens causing life-threatening nosocomial infections [1,2]. Typical clinical presentations of Klebsiella pneumonia are nosocomial respiratory tract infections, urinary tract infections, infections of the bloodstream and premature infant intensive care unit infections [1,3,4,5,6]. PDC represent the most potent producers of Interferon-alpha and play critical roles in antiviral immunity [20,21,22,23]. It has been reported that pDC sense skin injury and promote wound healing through type I interferon suggesting a novel role for these professional antigen presenting cells [24]. Klebsiella pneumoniae is a leading cause of severe hospital-acquired respiratory tract infections and death but little is known regarding the modulation of respiratory dendritic cell (DC) subsets. Plasmacytoid DC (pDC) are specialized type 1 interferon producing cells and considered to be classical mediators of antiviral immunity

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Conclusion