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Circulating CD1c+ myeloid dendritic cells are precursors to Langerhans cell histiocytosis (LCH) lesion CD1a+CD207+cells

ABSTRACT: Expression data from LCH lesion subpopulations and healthy donors' peripheral blood specimens Langerhans cell histiocytosis (LCH) is a myeloproliferative disorder that is characterized by the inflammatory lesions with pathogenic CD1a+CD207+ dendritic cells (DCs). BRAFV600E and other somatic activating MAPK gene mutations have been identified in differentiating bone marrow and blood myeloid cells, but the origin of the LCH lesion CD1a+CD207+DCs and mechanisms of lesion formation remain incompletely defined. In order to identify candidate LCH CD1a+CD207+DCs’ precursor populations, gene expression profiles of LCH lesion CD1a+CD207+DCs were first compared to established gene signatures from human myeloid cell subpopulations. Interestingly, the CD1c+ myeloid DC (mDC) gene signature was most enriched in the LCH CD1a+CD207+DC’ transcriptome. Additionally, the BRAFV600E allele was not only localized to CD1a+CD207-DCs and CD1a+CD207+DCs, but it was also identified in CD1c+mDCs in LCH lesions. Transcriptomes of CD1a+CD207-DCs were nearly indistinguishable from CD1a+CD207+DCs (both CD207low and CD207high subpopulations). Transcription profiles of LCH lesion CD1a+CD207+DCs and peripheral blood CD1c+mDCs from healthy donors were compared to identify potential LCH DC-specific biomarkers. HLADQB2 expression was significantly increased in LCH lesion CD1a+CD207+DCs compared to circulating CD1c+mDCs from healthy donors, and HLA-DQB2 antigen was identified on LCH lesion CD1a+CD207- and CD1a+CD207+DCs as well as on CD1c+(CD1a+CD207-) mDCs, but not in any other lesion myeloid subpopulations. Interestingly, HLADQB2 expression was specific to peripheral blood of patients with BRAFV600E+ peripheral blood mononuclear cells (PBMC), and HLA-DQB2+CD1c+blood cells were highly enriched for the BRAFV600E in these patients. These data support a model where blood CD1c+mDCs with activated ERK migrate to lesion sites where they differentiate into pathogenic CD1a+CD207+ DCs.

ORGANISM(S): Homo sapiens

PROVIDER: GSE122674 | GEO | 2020/01/21

REPOSITORIES: GEO

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Project description:Langerhans-cell histiocytosis (LCH) is characterized by heterogeneous lesions containing CD207+ Langerhans cells (LCs) and lymphocytes. In this study, we isolated CD207+ cells and CD3+ T cells from LCH lesions to determine cell-specific gene expression. Compared to control epidermal CD207+ cells, the LCH CD207+ cells yielded 2113 differentially-expressed genes (FDR<0.01). Surprisingly, expression of many genes previously associated with LCH, including cell-cycle regulators, pro-inflammatory cytokines and chemokines were not significantly different from control LCs in our study. However, several novel genes whose products activate and recruit T cells to sites of inflammation, including SPP1 (osteopontin), were highly over-expressed in LCH CD207+ cells. Furthermore, several genes associated with immature myeloid dendritic cells were over-expressed in LCH CD207+ cells. Compared to the peripheral CD3+ cells from LCH patients, the LCH lesion CD3+ cells yielded only 162 differentially-regulated genes (FDR<0.01), and the expression profile of the LCH lesion CD3+ cells was consistent with an activated regulatory T cell phenotype with increased expression of FOXP3, CTLA4 as well as SPP1. Based on these results, we propose a new model of LCH pathogenesis in which lesions do not arise from epidermal Langerhans cells, but from accumulation of bone-marrow derived immature myeloid dendritic cells that recruit activated lymphocytes. Cell-specific gene expression from LCH biopsy specimens was evaluated by comparing hybridization signal from amplified cDNA on Affymetrix gene chips (U133A Plus 2.0) (Table1). Three sets of comparisons were performed: 1) Thirteen LCH CD207+ samples were compared to 12 control skin LCH CD207+ samples. 2) Seven LCH lesion CD3+ samples were compared to 7 peripheral blood CD3+ samples from the same patients. 3) Twelve LCH lesion CD3+ samples were compared to 4 pooled control tonsil CD3+ samples (5 individual tonsil CD3+ samples/pool).

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Circulating CD1c+ myeloid dendritic cells are precursors to Langerhans cell histiocytosis (LCH) lesion CD1a+CD207+cells

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