CD14++CD16+ monocyte subset expansion in rheumatoid arthritis patients: Relation to disease activity and interleukin-17

Monocytes are divided into three major subsets based on the expression of the cluster of differentiation CD14 and CD16. The aim of this work was to determine which of the CD16+ monocyte subpopulations is expanded in rheumatoid arthritis (RA) and its association with disease activity and interleukin-17 (IL17) levels. Fifty-three RA patients and 20 controls were enrolled in this study. Flow cytometry was performed to detect monocyte subsets and IL17 was measured by ELISA. Disease activity score (DAS28) was assessed. CD14++CD16+ monocyte percentage was significantly higher in long standing RA patients compared with early patients and controls (p < 0.01, p < 0.001 respectively). It was significantly higher in patients with RA disease activity and remission compared with the controls (p < 0.001, p < 0.01 respectively). It was not significantly associated with resistance to disease modifying antirheumatic drugs (DMARDs), C-reactive protein, rheumatoid factor and anti-CCP positivity (p > 0.05). It significantly correlated with IL17 (p < 0.002). CD14+CD16+ monocyte percentage was not significantly correlated with any of the above parameters. IL17 level was significantly higher in patients with early and long standing RA compared to controls (p < 0.01, p < 0.001 respectively). IL17 was higher in RA patients with active disease compared to those in remission and controls (p < 0.01, p < 0.001 respectively). It was higher in RA patients resistant to DMARDs than in responding patients (p < 0.017). CD14++CD16+ monocyte subpopulation was expanded in long standing RA and was correlated with IL17 levels indicating its potential pathogenic importance in RA and may represent an attractive target for future therapeutic interventions.