Background Growth Arrest-Specific 6 (Gas6) and its receptor MERTK have been involved in the regulation of inflammation and apoptosis.

Objectives We evaluated if an impairment of Gas6/MERTK signalling system could be associated with Systemic Lupus Erythematosus (SLE) disease activity and, specifically, with kidney involvement.

Methods Gas6 and the soluble, cleaved form of MERTK (sMER) plasma concentration were measured in 59 SLE patients and in 46 healthy controls. Clinical and laboratory data were collected.

Results SLE patients had significantly higher plasma sMER concentrations (10,40 ng/ml [IQR 7,92–13,83] vs 2,65 ng/ml [2,38–3,23]) while healthy subjects showed only slightly higher plasma Gas6 concentrations than patients (22,8 ng/ml [IQR 19,2–24,7] vs 14,7 ng/ml [11,8–20,5]). Moreover, only sMER, but not Gas6, was significantly different being higher in SLE patients with renal involvement (11,3ng/mL [9,7–13,9ng/mL] vs 7,8 ng/mL [6,2–12,2ng/mL]). At univariate analysis sMER concentration was related to clinical and laboratory indexes of disease activity as SLEDAI, haemoglobin, ESR, proteinuria and creatinine plasma concentration but, at multiple regression analysis only 24 h urine protein concentration fitted the model (R=0,9751 F11,314; p<0,002).

Conclusions An increased sMER concentration can be detected in SLE patients, particularly those who showed renal involvement. Interestingly sMER is directly related to the degree of proteinuria, This observation suggests an increased cleavage of MERTK; on this basis an impairment of MERTK-mediated apoptotic bodies clearance could be supposed.

Disclosure of Interest None declared