Background/Purpose: Using whole exome sequencing (WES), we identified a de novo mutation in DYSF encoding dysferlin in 2 unrelated patients with systemic inflammation and sterile pulmonary abscesses. Unlike dysferlin mutations that cause muscular dystrophies, the patients have no muscle disease, but a robust clinical response to IL-1 blockade suggested inflammasome activation and the presentation with sterile pulmonary abscess formation raised questions about an efferocytosis defect

Methods: We characterized monocytes and neutrophil activation and function to assess the mechanism of the IL-1 dependent inflammation by flowcytometry, immunofluoroscence, ELISA, cytokine array, survival assay and we developed an efferocytosis assay. U937 cells expressing mutant cell line was used to further understand the mutation.

Results: Monocyte and monocyte-derived M1 and M2 macrophages (MDM) stimulated with LPS and ATP-released high IL-1 serum levels, that was higher in the DYSF patients’ monocytes and M1 and M2 MDM compared to healthy controls (HC), and was comparable to the augmented IL-1 production in NOMID. Dysferlin colocalizes with NLRP3 in LPS activated monocyte and in M1 and M2 MDMs. Expression levels of ASC, and Caspase-1 were increased in the DYSF patients monocytes. M2-MDMs from both patients expressed proinflammatory mediators, high CXCL1(P< 0.05), CCL2, IL-6 and IL-8. We observed LPS and ATP activation-induced altered nucleur integrity in M2-MDMs from both patients (70% and 50% respectively) compared to healthy controls. In neutrophils, LPS and ATP activation did not increase IL-1b was not upregulated although MIF, IL-16 and IL-8 levels were observed. We hypothesized that either delayed neutrophil apoptosis or clearence contribute to the lung abscess formation. While neutrophil apoptosis was normal, patients’ M2 MDM ability to clear healthy control neutrophils by efferocytosis was significantly impaired. Coculturing patients’ neutrophils with macrophages from healthy donors didn’t result in abnormal effereocytosis, thus suggesting an efferocytosis defect caused by mutant monocyte derived macrophages. The abnormal efferocyutosis was reproduced in dysferlin nutant U937 cells which showed a defect in phagosome maturation.

Conclusion: The de novo GOF mutation in dysferlin in two patients with systemic inflammation and sterile lung abscesses reveal a novel role of dysferlin in regulating inflammasome activation in monocytes and macrophage maturation and in neutriophil efferocytosis. Our data expand on a previously unidentified role of dysferlin in regulating M2-macrophage efferocytosis of neutrophils as a mechanisms for lung abscess formation.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/dysferlin-associated-autoinflammatory-disease-causing-systemic-inflammation-and-sterile-lung-abcesses-through-impaired-efferocytosis/