Effects of quinolones on granulocyte function in vitro

Granulocytes (PMN) play an important role in antibacterial host defence. The modulation of PMN-function by different antibiotics has been shown previously. Therefore, we investigated the possible immuno-modulatory effects of four new quinolone antibiotics: ciprofloxacin, norfloxacin, pefloxacin, ofloxacin. Pure PMN-preparations were obtained from healthy volunteers and incubated for 30 min at 37 degrees C with the different quinolones at different concentrations (0.1-1-5-10 mg/l). A complete PMN-functional profile was assayed. At all concentrations tested no significant differences were seen for myeloperoxidase content, superoxide production and chemiluminescence. A significant stimulation of phagocytosis and killing occurred at 10 mg/l of norfloxacin and at 10 mg/l of pefloxacin. An increase of chemotaxis towards formyl-methionyl-leucyl-phenylalanine was noted at 10 mg/l of ofloxacin, while stimulation of hexose monophosphate shunt was seen at 1 mg/l of ciprofloxacin and 10 mg/l of ofloxacin. The mechanism whereby both subinhibitory and inhibitory concentrations of quinolones moderately influence PMN-responsiveness is not yet known. Further studies are needed to elucidate the nature of this quinolone-effect and to assess its relevance in vivo.