Background Impaired phagocytosis of apoptotic bodies, inflammation and fibrosis are common features of Systemic Sclerosis (SSc)  and Sjögren Syndrome (SS) . The Gas6/TAM-system is involved in all these processes [3, 4].
Objectives To evaluate plasma Gas6 and sTAM receptors concentrations as putative biomarkers in SSc and SS.
Methods Forty-one consecutive patients with SSc (n.=23) or SS (n.=18) were recruited at a tertiary level rheumatology unit from December 2010 to May 2011; age-matched patients (n.=46) with degenerative joint disease served as controls. Relevant clinical data, including those on immunosuppressive therapies, comorbidities, physical examination, systolic pulmonary artery pressure (PAPs), ESR, CRP, C3, C4, modified Rodnan-skin-score, Valentini-score, Kazerooni-score, anti-centromere and/or anti-scl70 antibody positivity were recorded in a database. Plasma Gas6, sMer, and sAxl concentrations were measured by an ELISA method developed and validated at our laboratory  and by commercially available kits (R&D, USA), respectively. Non parametric, Pearson’s chi-square and multiple linear regression analyses were performed.
Results Subjects with SSc, SS and controls were similar for age, sex and comorbidities (autoimmune thyroid disease and hypertension) (Kruskaal-Wallis variance p>0.31). Median plasma Gas6 and sAxl were not different between groups (Kruskal-Wallis variance, p>0.05), while median plasma sMer was higher in SSc (3.5 ng/ml, 2.9-4.3 IQR) versus SS (3.3, 2.7-4.8) or controls (2.6, 2.4-3.2); post-hoc analysis p<0.009. At multiple linear regression analysis, plasma sMer correlated with PAPs (β=0.86, p=0.02) and ESR (β=0.18, p=0.05) but not with any other variables.
Conclusions Plasma sMer concentration is higher in SSc patients and associates with pulmonary arterial hypertension, but not with indexes of pulmonary fibrosis or scleroderma disease activity scores. The Gas6/Mer system may be relevant in the pathophysiology of pulmonary hypertension, possibly via the control of endothelial apoptosis.
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Disclosure of Interest None Declared
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