The role of interferon-mediated suppression of monocyte immunothrombosis in infection susceptibility in systemic lupus erythematosus.

Patients with systemic lupus erythematosus (SLE) exhibit significant susceptibility to severe bacterial infections, a leading cause of mortality. A key host defence mechanism is immunothrombosis, wherein activated monocytes rapidly upregulate tissue factor (TF) to initiate localized fibrin deposition that traps and contains pathogens. Effective immunothrombosis is therefore critical for preventing microbial dissemination. This process appears deficient in SLE, a disease defined by a systemic prothrombotic state, yet poor infection outcomes. A recently discovered molecular interaction suggests that TF directly binds to the interferon-α receptor (IFNAR1), acting as a rheostat to suppress interferon signalling. We hypothesize that in SLE, this regulatory axis is disrupted. The dominant, sustained interferon-stimulated gene (ISG) signatures in monocytes limit their capacity for TF upregulation in response to bacterial challenge, thereby impairing immunothrombosis and compromising bacterial containment. Supporting this, SLE patients with secondary antiphospholipid syndrome who have lower interferon signatures display markedly elevated TF levels and a different thrombotic profile, demonstrating the inverse relationship in a clinical subset. Furthermore, TF induction in monocytes is glycolysis-dependent, and SLE monocytes are known to have profound metabolic alterations. The chronic interferon state may thus impose a metabolic constraint that further limits the bioenergetic capacity for a robust TF response. Therefore, the confluence of interferon-driven suppression and metabolic dysfunction in SLE monocytes provides a compelling explanation for the failure of immunothrombosis, directly linking a core disease feature to infection susceptibility.