Genomics

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Pulmonary Eosinophilic Granulomatosis with Polyangiitis has IgG4 Plasma Cells and Immunoregulatory Features


ABSTRACT: The pathologic findings and immunologic mechanisms in eosinophilic granulomatosis with polyangiitis (EGPA) are poorly understood. To characterize pulmonary EGPA’s mechanisms, we examined EGPA paraffin-embedded lung biopsies by immunostaining, RNA sequencing, and reverse transcriptase PCR, compared to normal lung.  EGPA lung infiltrates had eosinophils, alveolar macrophages, B and T cells, plasma cells, basophils, and mast cells. Mast cell degranulation was sparse. PhosphoSMAD2 immunostaining suggests TGFβ activity. Using both immunostaining and RNA-sequencing, showed significant increases for both type 2 related genes (CD209, TNFSF14 (induces TGFβ and IL-13)), immunoregulatory genes (FOXP3, CYP27B1 (makes calcitriol), ALOX15 and particularly IGHG4). Regulatory T cells and IgG4 plasma cells with IgG4-containing presumed immune complexes coating macrophages, were strikingly abundant relative to controls. HPGD (metabolizes prostaglandins and other eicosanoids) was substantially decreased. RNA studies also showed increased contents of collagen transcripts, IL13, CCL18, and CCL13.  These findings suggest a novel mechanism involving alveolar macrophages, activated by ALOX15-eicosanoid products, making chemokines CCL18 and CCL13 and thus inducing a mixed type 2 plus immunoregulatory immune response. This infiltrate resembles the immune response to an invasive parasite rather than the IgE / mast cell degranulation response to luminal parasites or in asthma and other classic allergies. These findings also suggest new potential treatment targets for EGPA.

ORGANISM(S): Homo sapiens

PROVIDER: GSE144302 | GEO | 2020/01/28

REPOSITORIES: GEO

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