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

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.

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.

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.

b-FGF may participate in the inflammatory process by modulating the CR expression on blood monocytes.