Synovial fluid

Biology

Inflammatory bowel disease

Biochemistry

Rheumatoid arthritis

Immunology

Biomarker

Alternative medicine

Calprotectin

Osteoarthritis

Inflammation

Erythrocyte sedimentation rate

Internal medicine

S100A9

Medicine

Disease

S100A8

Pathology

Frontiers in Immunology

S100A9/S100A8 (calprotectin), a member of the S100 protein family, has been shown to play a pivotal role in innate immunity activation. Calprotectin plays a critical role in the pathogenesis of rheumatoid arthritis (RA), as it triggers chemotaxis, phagocyte migration and modulation of neutrophils and macrophages. Higher calprotectin levels have been found in synovial fluid, plasma, and serum from RA patients. Recent studies have demonstrated better correlations between serum or plasma calprotectin and composite inflammatory disease activity indexes than c-reactive protein (CRP) or the erythrocyte sedimentation rate (ESR). Calprotectin serum levels decreased after treatment, independently of the DMARD type or strategy. Calprotectin has shown the strongest correlations with other sensitive techniques to detect inflammation, such as ultrasound. Calprotectin independently predicts radiographic progression. However, its value as a biomarker of treatment response and flare after tapering is unclear. This update reviews the current understanding of calprotectin in RA and discusses possible applications as a biomarker in clinical practice.

From bench to bedside: Calprotectin (S100A8/S100A9) as a biomarker in rheumatoid arthritis