Macrophage migration inhibitory factor (MIF) seems to have an important function in the pathogenesis of granulomatosis with polyangiitis (GPA) according to the results of a new study. In patients with GPA, vasculitis is associated with the formation of inflammatory granulomas. “There remains a lack of clear understanding regarding the formation of granulomas in these patients,” explains corresponding author Antoine Sreih.

Credit: Springer Nature Limited

MIF is implicated in other granulomatous diseases, such as sarcoidosis and tuberculosis. “We used the comprehensive approach of combining a human genetic study with an experimental animal model to understand the role of MIF in GPA,” says Sreih.

Two MIF promoter polymorphisms have been identified: a -794 CATT6–8 microsatellite (rs5844572) and a -173 G/C SNP (rs755662). Thus, the researchers conducted a multicentre, cross-sectional genetic study of 501 patients with GPA and 576 healthy individuals. 60.2% of patients with GPA carried an increased number of -794 CATT6–8 repeats in their genome, compared with 53.9% of healthy individuals. Patients with GPA also had higher plasma levels of MIF than their disease-free counterparts.

“The experimental model is a mouse model of granulomatous vasculitis induced by injection of Candida albicans β-glucan,” explains Sreih. “To mimic the high-expression MIF polymorphisms in humans, we developed tissue-conditional transgenic mouse lines that overexpress MIF in lung epithelium.”

Mice overexpressing lung epithelial MIF developed more pulmonary granulomas than wild-type mice; they also had increased levels of neutrophil and macrophage chemokines and increased mortality. Injection of an anti-MIF monoclonal antibody reduced lung disease and improved survival in these mice.

Injection of an anti-MIF monoclonal antibody … improved survival in these mice

Notably, an anti-MIF receptor antibody is currently in phase II trials for the treatment of systemic lupus erythematosus, which, if successful, could have implications for the treatment of patients with GPA.