Basic fibroblast growth factor up-regulates the surface expression of complement receptors on human monocytes

Objective and Design: To clarify the possible involvement of basic fibroblast growth factor (b-FGF) in inflammation, we examined the effect of b-FGF on the surface expression of complement receptors (CR) on human monocytes in vitro.¶Materials and Methods: Heparinized venous blood was obtained from healthy adult donors. The surface expression of CR on blood monocytes was determined by two-color immunofluorescent staining using flow cytometry and monoclonal antibodies. A standard whole blood lysis technique was used to avoid any in vitro manipulation that would activate monocytes.¶Results: b-FGF increased the expression of CR3 on monocytes in a dose- and time-dependent manner. The b-FGF concentrations used were up to 100 ng/ml. The values of mean fluorescence intensity (MFI) of CR3 expression on unstimulated monocytes were 12.6 ± 1.3 (n=3), whereas those on b-FGF-stimulated monocytes were 59.2 ± 7.1 (n=3). b-FGF also up-regulated the expression of CR1 on monocytes in a dose- and time-dependent manner. The MFI values of CR1 expression on unstimulated monocytes were 2.5 ± 0.1 (n=3), whereas those on b-FGF-stimulated monocytes were 11.1 ± 0.6 (n=3). The magnitude of CR1 expression by monocytes was significantly smaller than that of CR3 expression. The maximal stimulatory effect of b-FGF on monocytes was observed using greater than 25 ng/ml of b-FGF and 90-120 min incubation period.¶Conclusion: b-FGF may participate in the inflammatory process by modulating the CR expression on blood monocytes.¶