To analyze lactoferrin expression on synovial fluid (SF) and peripheral blood neutrophils of patients with rheumatoid arthritis (RA) and to compare it with the lactoferrin expression on neutrophils from patients with osteoarthritis (OA).
Paired samples of peripheral blood and SF were obtained from 14 patients with RA and 9 patients with OA. Lactoferrin expression was evaluated on cell surfaces by cytofluorimetric analysis utilizing both polyclonal antibodies and the monoclonal anti-lactoferrin antibody AGM 2.29. Data are presented as mean fluorescence intensity.
In patients with RA, the expression of membrane lactoferrin was significantly increased on SF neutrophils in comparison with those in peripheral blood. This increase was found using both polyclonal antibodies and AGM 2.29 (p = 0.0001, p = 0.0017, respectively). In patients with OA, the difference was not significant. In addition, lactoferrin expression on SF neutrophils of patients with RA was significantly increased compared with that found on SF neutrophils of patients with OA (polyclonal antibodies, p = 0.0015; AGM 2.29, p = 0.005). In patients with RA, no correlation was found between lactoferrin expression and disease activity.
Our results provide evidence for an activation of neutrophil granulocytes at site of inflammation in RA and indicate that lactoferrin surface expression represents a reliable neutrophil activation marker.