IgA antibodies against oxidation-specific epitopes are generated by double negative B cells and are associated with impaired lung function in fibrotic interstitial lung diseases.

Abstract

BackgroundFibrotic interstitial lung diseases (fILD) are characterized by progressive scarring of the lung and high mortality. Oxidation-specific epitopes (OSEs) form on oxidized lipids and proteins, are abundant in lungs of patients with fILD and perpetuate lung injury and fibrosis in animal models. OSE-targeting antibodies bind to OSEs and modulate their downstream effects. The objective of this study was to determine the association of OSE-targeting antibodies with lung function and other clinical outcomes, and to characterize OSE-specific B cell phenotypes in fILD. MethodsTo determine the association of OSE-targeting antibodies and clinical outcomes in fILD, we measured plasma levels of OSE-specific antibodies against the malondialdehyde modified LDL mimotope P1 and anti-ApoB100 immune complex (anti-ApoB100 IC) in patients with fILD and age-matched controls. We then performed B cell phenotyping of patients with idiopathic pulmonary fibrosis (IPF) and healthy controls utilizing mass cytometry time of flight (CyTOF). To investigate effects of pro-fibrotic mediators on anti-OSE IgA antibody production, we measured B cell responses to OSEs in vitro. ResultsCohort of 109 patients with fILD (Hypersensitivity Pneumonitis, Idiopathic Pulmonary Fibrosis, Nonspecific Interstitial Pneumonia, Connective Tissue Disease-Associated Interstitial Lung Disease) and 55 healthy donors, and a second cohort of 20 patients with IPF and 9 healthy donors were included in the study. OSE-specific antibody levels anti-P1 and anti-ApoB100 IC IgA and IgG were significantly elevated in participants with fILD compared to healthy donors (p<0.0001). Higher anti-OSE IgA was associated with worse baseline lung function, including forced vital capacity (FVC) (p<0.001) and diffusing capacity for carbon monoxide (DLCO) (p<0.01). IgA+CD27-CD21-CD11c+ double negative type 2 (DN2) B cells correlated with anti-OSE IgA levels (p<0.05) and were enriched in OSE-specific cells. DN2 B cell precursors, CXCR5-CD11c+ naive B cells and IgA+CD27-CD21-CD11c- DN3 B cells, were significantly expanded in IPF compared to healthy donors. Both DN2 and DN3 B cells correlated with plasmablast pools in IPF patients and showed high baseline levels of IL-21 receptor, which was reduced in more differentiated cells. TGF-{beta} combined with OSEs, but not OSEs alone, induced OSE-specific IgA production in vitro. ConclusionsCirculating anti-OSE IgA antibodies are elevated in patients with fibrotic ILDs regardless of underlying pathology and negatively correlate with lung function. These antibodies correlated with the DN2 B cell subset which was enriched in OSE-specific cells. Phenotypic analysis of B cell subsets showed expression of markers consistent with DN to plasmablast differentiation. Finally, TGF-{beta} promoted OSE-IgA production in vitro. These findings show a novel link between oxidative tissue damage, anti-OSE antibodies and DN2 B cells in fILD which may provide opportunities for new targeted therapies.