Exploring complement biomarkers in suspected axial spondyloarthritis

Area of Science:

• Immunology
• Rheumatology
• Biochemistry

Background:

• Axial spondyloarthritis (axSpA) is a chronic inflammatory disease.
• Biomarkers are needed for early diagnosis and understanding axSpA pathogenesis.
• The lectin pathway of complement activation (LPCA) plays a role in innate immunity and inflammation.

Purpose of the Study:

• To investigate lectin pathway proteins (LPPs) as potential biomarkers for axial spondyloarthritis (axSpA).
• To compare LPP levels in patients with axSpA and chronic low back pain (cLBP).
• To assess the diagnostic potential of LPPs in axSpA.

Main Methods:

• Serum samples from 515 participants (151 axSpA, 364 cLBP) were analyzed using immunoassays.
• Measurements included mannan-binding lectin (MBL), collectin liver-1 (CL-L1), ficolins, MBL-associated serine proteases (MASPs), and C3dg.
• Statistical analyses included univariate and multivariate logistic regression, adjusted for C-reactive protein (CRP).

Main Results:

• Serum levels of L-ficolin, MASP-2, and C3dg were elevated in axSpA patients.
• MASP-3 and CL-L1 levels were decreased in axSpA patients.
• C3dg and MASP-3 levels remained significant predictors of axSpA diagnosis after CRP adjustment.

Conclusions:

• Serum C3dg and MASP-3 levels differ significantly between axSpA and cLBP patients, even after CRP adjustment.
• While combining LPPs with HLA-B27 improved specificity, it reduced sensitivity for axSpA diagnosis.
• The findings suggest a role for complement activation, specifically C3dg and MASP-3, in axSpA pathogenesis.