Human Lung Fibroblasts Present Bacterial Antigens to Autologous Lung Th Cells

Abstract

Lung fibroblasts are key structural cells that reside in the submucosa where they are in contact with large numbers of CD4 Th cells. During severe viral infection and chronic inflammation, the submucosa is susceptible to bacterial invasion by lung microbiota such as nontypeable Haemophilus influenzae (NTHi). Given their proximity in tissue, we hypothesized that human lung fibroblasts play an important role in modulating Th cell responses to NTHi. We demonstrate that fibroblasts express the critical CD4 T cell Ag-presentation molecule HLA-DR within the human lung, and that this expression can be recapitulated in vitro in response to IFN-γ. Furthermore, we observed that cultured lung fibroblasts could internalize live NTHi. Although unable to express CD80 and CD86 in response to stimulation, fibroblasts expressed the costimulatory molecules 4-1BBL, OX-40L, and CD70, all of which are related to memory T cell activation and maintenance. CD4 T cells isolated from the lung were predominantly (mean 97.5%) CD45RO memory cells. Finally, cultured fibroblasts activated IFN-γ and IL-17A cytokine production by autologous, NTHi-specific lung CD4 T cells, and cytokine production was inhibited by a HLA-DR blocking Ab. These results indicate a novel role for human lung fibroblasts in contributing to responses against bacterial infection through activation of bacteria-specific CD4 T cells.

Manning the Barricades: Lung Fibroblasts and CD4+ T Cells as the Last Line of Defense against Bacterial Invasion?

“…Th1>Th17>T-regulatory (Treg) cells>Th2. 56 Additionally, this work confirmed that naive cells are rare within the peripheral lung environment and that CD45RO+CCR7-effector memory cells predominated, making up approximately 80% of T cells found in the lung, with the majority of the remainder being central memory cells. 7,56,57 An important difference between naïve and memory T cells is their requirement for costimulatory signals.…”

“…56 Additionally, this work confirmed that naive cells are rare within the peripheral lung environment and that CD45RO+CCR7-effector memory cells predominated, making up approximately 80% of T cells found in the lung, with the majority of the remainder being central memory cells. 7,56,57 An important difference between naïve and memory T cells is their requirement for costimulatory signals. While naïve T cells are recognised as having an absolute requirement for signalling through CD28-CD80/86 interaction, it has been shown that memory T cell populations do not necessarily require this interaction to reactivate.…”

“…72 Fibroblasts have been demonstrated to express detectable levels of MHC II molecules in situ in the eye, skin and lung. 56,[73][74][75] However, analysing the ability of fibroblasts to act as APCs to CD4+ T cells was hampered by the lack of fibroblast expression of MHC II molecules when these cells were cultured in vitro. Such differences could be explained by the very act of culturing these cells as there are substantial differences in fibroblast phenotype dependent upon whether they are cultured in 2D tissue culture plates or 3D matrix cultures.…”

“…Treatment of fibroblasts with recombinant IFNγ is now routinely used to enable investigation of interactions with T cells; demonstrating that in addition to dermal fibroblasts, synovial and lung fibroblasts can also activate CD4+ T cells particularly those T cells inhabiting tissue zones with an activated memory phenotype. 56,79,80,81 However, addition of exogenous IFNγ is not always necessary to model these effects, again demonstrating the range of responses that can be observed from fibroblasts derived from different sources. Indeed, corneal fibroblasts have been shown to be able to make their own IFNγ when exposed to LPS derived from the lung pathogen Pseudomonas aeruginosa.…”

Versatile workflow for cell type resolved transcriptional and epigenetic profiles from cryopreserved human lung

“…Primary human lung fibroblasts were isolated by explant outgrowth from fresh or cryopreserved tumor-free tissue derived from distal airway-free lung tissue (parenchymal fibroblasts) or from small airways (peribronchial fibroblasts) following published protocols 25,52-54 . Cells were collected from several explant pieces to preserve heterogeneity HLF were maintained in 2% FBS DMEM ++ ( Table S3 ) and used within passages 2-4.…”