Elevation of Metrnβ and Its Association with Disease Activity in Systemic Lupus Erythematosus.

Systemic lupus erythematosus (SLE) is an auto-immune disease, the pathogenesis of which remains to be fully addressed. Metrnβ is a novel cytokine involved in the pathogenesis of inflammatory disease, but its regulatory roles in SLE are unclear. We aimed to comprehensively investigate the clinical value of Metrnβ in SLE. A massive elevation of circulating Metrnβ levels was observed in SLE, and patients with an active phase displayed higher Metrnβ concentrations than those with inactive phases. Additionally, we found that Metrnβ expression was positively correlated with clinical indicators of SLE. Longitudinal cytokine and chemokine profiles revealed a disturbed immune response in SLE, with high activity profiles displayed severe pathogenic inflammation, and a positive correlation of the serum Metrnβ with CXCL9, IL10, IL18 and IL1RA was observed as well. Moreover, Metrnβ expressions exhibited an inverse correlation with Treg and B10. Of note, a significant decrease of ILC2 was found in SLE, and there was a negative correlation of Metrnβ with ILC2 as well. Further ROC analysis showed that the area under the curve (AUC) for Metrnβ was 0.8250 (95% CI: 0.7379-0.9121), with a cutoff value of 1131 pg/mL to effectively distinguish SLE patients from healthy controls. Our study herein demonstrated for the first time that Metrnβ values were increased and were immunologically correlated with SLE activity, which could be utilized as an alternative biomarker for the early identification and predicting of the immuno-response of SLE.