Plasmacytoid dendritic cell number, blood IFNα and anti-nuclear antibody positivity in infliximab-treated rheumatoid arthritis patients. (a) Circulating plasmacytoid dendritic cell (pDC) levels in rheumatoid arthritis (RA) patients after 14 weeks of infliximab therapy. pDC subsets were measured in the peripheral blood of patients, and two groups were individualized: patients with positive anti-nuclear antibody (ANA) (ANApos, n = 30) and patients with negative ANA (ANAneg, n = 16). Mean ± standard deviation shown. *P < 0.01, Mann–Whitney U test. (b) Correlation between ANA levels and pDC variations under infliximab therapy. ANA levels (1/dilution) and the pDC amount were measured on the same blood draw, before each infliximab infusion. (c) Detecting IFNα in serum of RA patients treated by infliximab and developing or not ANA. IFNα levels (pg/ml) were measured in peripheral blood of RA patients under infliximab therapy with ANA (n = 30) or without ANA (n = 16). *P < 0.001, Mann–Whitney U test.