OBJECTIVE: To examine whether proteins of the lectin pathway of the complement system are involved in systemic lupus erythematosus (SLE) pathogenesis.

METHODS: Using time-resolved immunofluorometric assays, plasma levels of mannan-binding lectin (MBL)-associated serine proteases 1 (MASP-1), MASP-2, MASP-3, MBL-associated protein of 19 kDa (MAp19), and MAp44 were determined in 58 patients with SLE and 65 healthy controls (HC).

RESULTS: Plasma concentrations in patients with SLE were higher than HC regarding MASP-1, MASP-3, and MAp44 (p < 0.0001, 0.0003, and 0.0013). Complement factor 3 correlated negatively and anti-dsDNA positively with levels of MAp19 (p = 0.0035, p = 0.0133).

CONCLUSION: In SLE, plasma levels of MASP and MAp are altered and associated with SLE characteristics, supporting a role in SLE pathogenesis.