Enhanced repopulation of murine hematopoietic organs in sublethally irradiated mice after treatment with ciprofloxacin

We analyzed the effect of ciprofloxacin, fleroxacin, and ceftazidime on production of colony-stimulating factors (CSF) by cultured murine spleen cells in the presence of pokeweed mitogen (PWM). Ciprofloxacin at concentrations of 5 to 10 micrograms/mL in concert with PWM stimulated CSF production by cultured spleen cells. A 3.5-fold increase in the number of CFU-C was observed in the presence of ciprofloxacin- PWM spleen conditioned medium (SCM) as compared with control cultures exposed to PWM-SCM only. Antimurine GM-CSF and antimurine interleukin-3 (IL-3) antibodies inhibited colony formation stimulated by PWM-SCM or ciprofloxacin-PWM-SCM. Fleroxacin and ceftazidime at concentrations of 1 to 100 micrograms/mL and ciprofloxacin at high concentration (greater than 10 micrograms/mL) either did not affect CSF production by spleen cells or had an inhibitory effect. In vivo treatment of sublethally irradiated (650 rad) mice with ciprofloxacin (15 mg/kg per dose three times daily for 5 days) resulted in an increased number of myeloid progenitors in the spleen and bone marrow (BM) of treated mice. In contrast, treatment with ceftazidime did not affect progenitor cell numbers. On days 4 and 8 postirradiation ciprofloxacin-treated mice had a 2.3- and 3.8-fold increase, respectively, in the number of CFU-C in the BM. The number of CFU-C in the spleen did not increase on day 4 postirradiation, but on day 8, the number increased 1.7-fold. On day 4 postirradiation, sublethally irradiated mice treated with ciprofloxacin had a higher WBC count, RBC count, and hemoglobin level as compared with ceftazidime- and saline-treated mice. Twenty-four days postirradiation, 45% of saline-treated mice (20 of 44), and 35% of ceftazidime-treated mice (8 of 23) died, as compared with 13% (5 of 38) of ciprofloxacin-treated mice (P less than .05). These studies indicate that ciprofloxacin may have an immune-enhancing effect on the hematopoietic system in neutropenic mice.