ABSTRACT
Macrophages regulate protective immune responses to infectious microbes, but aberrant macrophage activation frequently drives pathological inflammation. To identify regulators of vigorous macrophage activation, we analyzed RNA-seq data from synovial macrophages and identified SLAMF7 as a receptor associated with a superactivated macrophage state in rheumatoid arthritis. We implicated IFN-γ as a key regulator of SLAMF7 expression and engaging SLAMF7 drove a strong wave of inflammatory cytokine expression. Induction of TNF-α after SLAMF7 engagement amplified inflammation through an autocrine signaling loop. We observed SLAMF7-induced gene programs not only in macrophages from rheumatoid arthritis patients but also in gut macrophages from patients with active Crohn's disease and in lung macrophages from patients with severe COVID-19. This suggests a central role for SLAMF7 in macrophage superactivation with broad implications in human disease pathology.
Subject(s)
Inflammation/immunology , Macrophage Activation/immunology , Signaling Lymphocytic Activation Molecule Family/immunology , Transcriptome/immunology , Acute Disease , Adult , Arthritis, Rheumatoid/genetics , Arthritis, Rheumatoid/immunology , Arthritis, Rheumatoid/metabolism , COVID-19/genetics , COVID-19/immunology , COVID-19/metabolism , COVID-19/virology , Cells, Cultured , Chronic Disease , Crohn Disease/genetics , Crohn Disease/immunology , Crohn Disease/metabolism , Female , Humans , Inflammation/genetics , Inflammation/metabolism , Macrophage Activation/genetics , RNA-Seq/methods , Reverse Transcriptase Polymerase Chain Reaction/methods , SARS-CoV-2/immunology , SARS-CoV-2/physiology , Signaling Lymphocytic Activation Molecule Family/genetics , Signaling Lymphocytic Activation Molecule Family/metabolism , Single-Cell Analysis/methods , Synovial Membrane/immunology , Synovial Membrane/metabolism , Synovial Membrane/pathology , Transcriptome/geneticsABSTRACT
We explored the potential link between chronic inflammatory arthritis and COVID-19 pathogenic and resolving macrophage pathways and their role in COVID-19 pathogenesis. We found that bronchoalveolar lavage fluid (BALF) macrophage clusters FCN1+ and FCN1+SPP1+ predominant in severe COVID-19 were transcriptionally related to synovial tissue macrophage (STM) clusters CD48hiS100A12+ and CD48+SPP1+ that drive rheumatoid arthritis (RA) synovitis. BALF macrophage cluster FABP4+ predominant in healthy lung was transcriptionally related to STM cluster TREM2+ that governs resolution of synovitis in RA remission. Plasma concentrations of SPP1 and S100A12 (key products of macrophage clusters shared with active RA) were high in severe COVID-19 and predicted the need for Intensive Care Unit transfer, and they remained high in the post-COVID-19 stage. High plasma levels of SPP1 were unique to severe COVID-19 when compared with other causes of severe pneumonia, and IHC localized SPP1+ macrophages in the alveoli of COVID-19 lung. Investigation into SPP1 mechanisms of action revealed that it drives proinflammatory activation of CD14+ monocytes and development of PD-L1+ neutrophils, both hallmarks of severe COVID-19. In summary, COVID-19 pneumonitis appears driven by similar pathogenic myeloid cell pathways as those in RA, and their mediators such as SPP1 might be an upstream activator of the aberrant innate response in severe COVID-19 and predictive of disease trajectory including post-COVID-19 pathology.