CD103+ Dendritic Cells Control Th17 Cell Function in the Lung

Th17 cells express diverse functional programs while retaining their Th17 identity, in some cases exhibiting a stem-cell-like phenotype. Whereas the importance of Th17 cell regulation in autoimmune and infectious diseases is firmly established, the signaling pathways controlling their plasticity are undefined. Using a mouse model of invasive pulmonary aspergillosis, we found that lung CD103+ dendritic cells (DCs) would produce IL-2, dependent on NFAT signaling, leading to an optimally protective Th17 response. The absence of IL-2 in DCs caused unrestrained production of IL-23 and fatal hyperinflammation, which was characterized by strong Th17 polarization and the emergence of a Th17 stem-cell-like population. Although several cell types may be affected by deficient IL-2 production in DCs, our findings identify the balance between IL-2 and IL-23 productions by lung DCs as an important regulator of the local inflammatory response to infection

Human fetal dendritic cells promote prenatal T-cell immune suppression through arginase-2.

During gestation the developing human fetus is exposed to a diverse range of potentially immune-stimulatory molecules including semi-allogeneic antigens from maternal cells, substances from ingested amniotic fluid, food antigens, and microbes. Yet the capacity of the fetal immune system, including antigen-presenting cells, to detect and respond to such stimuli remains unclear. In particular, dendritic cells, which are crucial for effective immunity and tolerance, remain poorly characterized in the developing fetus. Here we show that subsets of antigen-presenting cells can be identified in fetal tissues and are related to adult populations of antigen-presenting cells. Similar to adult dendritic cells, fetal dendritic cells migrate to lymph nodes and respond to toll-like receptor ligation; however, they differ markedly in their response to allogeneic antigens, strongly promoting regulatory T-cell induction and inhibiting T-cell tumour-necrosis factor-α production through arginase-2 activity. Our results reveal a previously unappreciated role of dendritic cells within the developing fetus and indicate that they mediate homeostatic immune-suppressive responses during gestation

C3^−/− mice show greater weight loss and mortality during influenza infection.

<p>(<b>A</b>) Percentage of body weight loss after influenza infection. A weight loss of <20% and recovery represents a sub-lethal infection. (<b>B</b>) Survival curve comparing WT and C3^−/− mice during influenza infection (n = 6–7 in each group). (<b>C</b>) Plots represent <i>ex vivo</i> analysis of CFSE-labeled OT-I CD8⁺ T cell proliferation in the dLN 3 days after infection with PR8 and PR8-OT-I (bottom). The graph on the right shows the respective division index for the proliferating OT-I CD8⁺ T cells for each group of mice. (<b>D</b>) Plots represent <i>ex vivo</i> analysis of CFSE-labeled OT-II CD4⁺ T cell proliferation in the dLN 3 days after infection with PR8 and PR8-OT-II (bottom). The graph on the right shows the respective division index for the proliferating OT-II CD4⁺ T cells for each group of mice. (<b>E</b>) Histogram showing expression of costimulatory molecules CD86, CD80 and CD40 on CD103⁺ DCs and CD11b⁺ DCs in the dLN on day 2 post infection. Filled histogram: Isotype control, dashed histogram: Naïve, open histogram: infected. (<b>F</b>) Bar graphs show the mean fluorescent intensity (MFI) of CD86, CD80 and CD40 expression on CD103⁺DC and CD11b⁺ DC subsets in the dLN of naïve and influenza infected (Day 2) WT or C3^−/− mice. (<b>G</b>) Plots represent CFSE-labeled OT-I CD8⁺ T cell proliferation 3 days after co-culture with sorted CD103⁺ DCs and CD11b⁺ DCs obtained from pooled dLN of PR8-OT-I influenza infected mice at a ratio of 1∶10 (DC:T cells). Results shown are representative of four experiments with similar results. The values are expressed as mean ± SEM.</p

C3^−/− mDCs display similar capacity for virus uptake and maturation.

<p>(<b>A</b>) Dot plots show the percentage of DiD flu⁺ uptake by CD103⁺ DC (left panel) and CD11b⁺ DC (right panel) in WT and C3^−/− mice 16 hrs after DiD flu administration on day 1 post infection with PR8. (<b>B</b>) Bar graph shows the average numbers of DiD flu⁺ CD103⁺ DCs and DiD flu⁺ CD11b⁺ DCs in the lungs of WT and C3^−/− mice. (<b>C</b>)Single cell preparations from the lungs were enriched for DCs by a density gradient method. Enriched DCs were infected with influenza virus under <i>ex vivo</i> culture conditions and six hours later the CD103⁺ and CD11b⁺ DCs were flow sorted. Q-RT-PCR for the indicated cytokines were performed on the RNA obtained from the CD103⁺ and CD11b⁺ DC populations. Bar graph shows % relative expression in comparison to un-infected control. (<b>D</b>) WT and C3^−/− mice were infected with flu and 24 hours later the CD103⁺ and CD11b⁺ DCs from the lungs were flow sorted. Q-RT-PCR for the indicated cytokines were performed on the RNA obtained from the CD103⁺ and CD11b⁺ DC populations. Bar graph shows % relative expression in comparison to un-infected control. (<b>E</b>) Bar graphs shows the mean fluorescent intensity of CD86, CD40 and CD80 expression on CD103⁺DC and CD11b⁺ DC subsets in the lungs of naïve and PR8 infected WT or C3^−/− mice. The data are representative of three different experiments with similar results. The values are expressed as mean ± SEM.</p

Migratory DC subsets are reduced in the dLN in C3^−/− mice after influenza infection.

<p>(<b>A</b>) Kinetics of CD103⁺ DCs and CD11b⁺ DCs in the lungs during influenza infection in WT and C3^−/− mice. Populations were gated as show in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1003115#ppat.1003115.s002" target="_blank">Fig. S2</a>. Numbers within the dot plot represent average percentage of cells for the group. (<b>B</b> and <b>C</b>) Absolute numbers of CD103⁺ DC (<b>B</b>) and CD11b⁺ DC (<b>C</b>) subsets in lungs during steady state and during influenza infection. (<b>D</b>) Kinetics of CD103⁺ DCs and CD11b⁺ DCs in the dLN during influenza infection in WT and C3^−/− mice. Populations were gated as shown in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1003115#ppat.1003115.s001" target="_blank">Fig. S1</a>. Numbers within the dot plot represent average percentage of cells for the group. (<b>E</b> and <b>F</b>) Absolute numbers of CD103⁺ DC (<b>E</b>) and CD11b⁺ DC (<b>F</b>) subsets in dLN during steady state and during influenza infection. The values are expressed as mean ± SEM. The data are representative of three different experiments with similar results. *, P<0.05, and **P<0.01.</p

Langerin-DTR mice show effector T cells response and survival characteristics similar to those of C3^−/− mice upon influenza infection and has defective CD11b⁺ DC migration.

<p>(<b>A</b>) Plots represent <i>ex vivo</i> analysis of CFSE-labeled OT-I CD8⁺ T cells proliferation in the dLN 3 days after infection with PR8 and PR8-OT-I (bottom) in WT and CD103⁺ DCs depleted langerin-DTR mice. (<b>B</b>) Percentage of body weight loss after influenza infection. (<b>C</b>) Survival curve comparing WT, C3^−/− and Langerin –DTR mice during influenza infection (n = 6 per group). (<b>D</b>) Graph shows the relative mRNA expression level of influenza M protein in lung tissues of WT and CD103⁺ DCs depleted langerin-DTR mice infected with 4 PFU of PR8. (<b>E</b>) Graph shows the frequency of IFNγ secreting CD4⁺ T cells in lungs by <i>ex vivo</i> overnight stimulation with MHC-II flu peptide on day 7 post infection. (<b>F</b>) Bar graph shows the absolute numbers of IFNγ secreting CD4⁺ T cells in lungs on day 7 post infection (<b>G</b>) Graph shows the frequency of Flu specific CTL response in lung as measured by Flu _peptide (ASNENMETM (NP _366–374)/H-2D^b tetramer staining on day 7 post infection. (<b>H</b>) Bar graph shows the absolute numbers of flu specific CD8⁺ T cells in lungs by tetramer staining on day 7 post infection. DT treated WT and Langerin-DTR mice were flu infected and the migration of CD103⁺ and CD11b⁺ DCs were evaluated as described before on day 3 post infection. (<b>I</b>) Dot plots show CD103⁺ and CD11b⁺ DCs mDCs in the dLN of DT treated and untreated WT and Langerin-DTR mice. Numbers within the dot plot represent cell number. (<b>J</b>) Total number of CD103⁺(top) and CD11b⁺(bottom) DCs in the dLN of flu infected mice. Results shown are representative of at least three different experiments with similar results. The values are expressed as mean ± SEM.</p

Complement Mediated Signaling on Pulmonary CD103+ Dendritic Cells Is Critical for Their Migratory Function in Response to Influenza Infection

10.1371/journal.ppat.1003115PLoS Pathogens91