Antibody-opsonized extracellular traps modulate macrophage responses and attenuate their T cell-associated inflammatory and costimulatory characteristics.

Macrophages and neutrophils coordinate inflammatory and reparative immunity, and dysregulated interactions between these cells contribute to the pathogenesis of immune-mediated inflammatory diseases. While extracellular traps (ETs), formed by neutrophils and other leukocytes, are enriched in citrullinated histones and exert significant pro-inflammatory effects, it remains unclear how distinct macrophage subsets interpret and resolve ET-derived signals. Here we show that macrophage subsets consistent with pro-inflammatory (GM-CSF + LPS + IFN-γ differentiated) or inflammation-resolving (M-CSF + IL-4 differentiated) characteristics, differentially engage with neutrophil-derived ETs and that antibody binding to ETs reshapes these interactions. ETs induce the release of pro-inflammatory cytokines and chemokines in both macrophage subtypes. While inflammation-resolving macrophages readily phagocytose ETs, pro-inflammatory macrophages exhibit limited uptake. Fc domain-dependent ET phagocytosis by both macrophage subsets is significantly enhanced when ETs are opsonized with an anti-citrullinated histone H2A and H4 monoclonal antibody. Opsonized ETs upregulate macrophage expression of genes encoding negative regulators of Mitogen-Activated Protein Kinase (MAPK) signaling and reduce expression of genes encoding pro-inflammatory receptors. Exposure to antibody-opsonized ETs following macrophage activation with LPS and IFN-γ attenuates the T cell-associated features of pro-inflammatory macrophages with reduced surface expression of CD80 and CD86 and decreased secretion of IL-12 and CXCL9. In inflammation-resolving macrophages antibody-opsonized ETs attenuate MAPK-dependent Toll-like receptor responses and inhibit secretion of CXCL9 and CXCL10 while enhancing IL-10 secretion. Together, these findings describe the pro-inflammatory impact of neutrophil-derived ET exposure on macrophages and delineate a previously unrecognized regulatory axis by which antibodies targeting ET components modulate macrophage responses across distinct subsets to attenuate their T cell-associated inflammatory and costimulatory responses, indicating relevance for therapeutic strategies aimed at modulating ET-driven inflammation.