Objective: To investigate periodic disturbances in proinflammatory activation of neutrophils and monocytes in patients with familial Mediterranean fever (FMF) both during an attack and in remission.
Methods: 20 FMF patients, who were naive to colchicine treatment and did not have amyloidosis, and 10 patients with Behçet's disease (BD) were enrolled in this study. Phagocytosis, respiratory burst, CD11a/CD18 expression and intracellular cytokine synthesis were determined by flow cytometry. Endotoxin tolerance induction was defined by a reduced capacity of monocytes to respond to lipopolysaccharide (LPS) activation following a first exposure to LPS.
Results: In FMF patients, we observed upregulation of neutrophil and monocyte phagocytic activity and oxidative burst during remission and downregulation of phagocytic activity and stimulus-dependent oxidative burst during an attack. A comparative analysis of oxidative burst has revealed that while the neutrophil population shows a certain periodicity in the increase (during remission) and decrease (during attacks) in the spontaneous and inducible respiratory burst, periodicity in the monocyte population is very poor. In addition, LPS-induced oxidative burst and CD11a/CD18 integrin surface expression is higher in patients during an attack compared to patients in remission. The induction of homologous tolerance of monocytes to the repeated action of LPS is observed in FMF patients during an attack, normal donors and patients with BD, whereas monocytes from patients in remission failed to induce LPS homologous tolerance and exhibited heightened sensitivity to bacterial endotoxin. We found that colchicine is able to restore impaired LPS homologous tolerance induction in FMF patients in remission upon increased synthesis of IL-4 in FMF patient monocytes.
Conclusion: Chronic inflammation during FMF is characterized by periodic changes in monocyte and neutrophil activation and heightened sensitivity to endotoxin, which is associated with the episodic nature of FMF. Increased endotoxin sensitivity in the period of remission could result from a shift in the monocyte activation program from 'alternatively' into 'classically' activated monocytes, which may have important implications for the treatment of FMF.