Background Systemic Lupus Erythematosus (SLE) is a systemic autoimmune disease characterized by the production of autoantibodies. We aimed to find salivary protein biomarkers in Korean patients with SLE.

Methods The salivary proteins were subjected to 2-dimensional gel electrophoresis (2-DE). The spots exhibiting >2-fold intensity change between SLE and healthy subjects (HSs) were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MS) analysis. The amounts of candidate proteins in saliva of patients with SLE and rheumatoid arthritis (RA), and HSs were analyzed using western blotting and enzyme-linked immunosorbent assay.

Results The proteomic analysis using 2-DE and MS revealed 10 differentially expressed protein spots, which included immunoglobulin gamma-3 chain C (IGHG3), protein S100, lactoferrin, leukemia-associated protein 7, and 8-oxoguanine DNA glycosylase. The patients with SLE exhibited enhanced salivary IGHG3 (3.9 ± 2.15 pg/mL) and lactoferrin (4.7 ± 1.8 pg/mL) levels than patients with rheumatoid arthritis (RA) (1.8 ± 1.01 pg/mL and 3.2 ± 1.6 pg/mL, respectively, p<0.001 for both) or HCs (2.2 ± 1.64 pg/mL and 2.2 ± 1.7 pg/mL, respectively, p<0.001 for both). The levels of salivary IGHG3 correlated with erythrocyte sedimentation rate (r =0.26, p =0.01), anti-dsDNA antibody levels (r =0.25, p =0.01), and nephritis (r =0.28, p =0.01).

Conclusions The levels of salivary IGHG3 and lactoferrin were higher in patients with SLE. In addition, salivary IGHG3 levels correlated with SLE disease activity markers.

Acknowledgements This research was supported by a grant from the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health & Welfare, Republic of Korea (HI16C0992).