Up-regulated dipeptidyl-peptidase IV (CD26) on monocytes was unaffected by effective DMARD treatment in early steroid and DMARD-naive rheumatoid arthritis.

OBJECTIVES: To study the CD26 density on monocytes and CD4+ T-lymphocytes in steroid and DMARD-naïve, early rheumatoid arthritis (RA) patients and to analyse for correlations with disease activity, including long-term radiographic progression. METHODS: Forty patients with active, early steroid and DMARD naïve RA (<6 months' duration) were randomised to treatment with methotrexate (MTX) versus MTX and cyclosporine A (CYA). Controls were 15 healthy age and gender matched subjects. Peripheral blood mononuclear cells were analysed for CD26 density by flow cytometry at baseline and after 52 weeks. Radiographic progression was scored by delta total Sharp-van der Heijde score (TSS) from 0 to 5 years. RESULTS: The density of CD26 on monocytes (CD3-CD14+) in RA was up-regulated compared to healthy controls (p<0.0001) and remained unaffected by clinically effective DMARD treatment after 52 weeks. In anti-CCP positive RA patients (n=18) baseline CD26 density on monocytes correlated to 5-year radiographic progression (p=0.008, r=0.60). The density of CD26 did not correlate to DAS28, the swollen or tender joint count or CRP-level at baseline or at year one. The CD26 density on CD4+ T-lymphocytes at week 0 was comparable to healthy controls (p=0.34). CONCLUSIONS: The up-regulated density of CD26 on monocytes in steroid and DMARD naïve active early RA was unaffected by 52 weeks of effective DMARD treatment and correlated to 5-year radiographic progression.