INDUCTION OF LUNG EOSINOPHILIA AND NEUTROPHILIA IN GUINEA-PIGS FOLLOWING INJECTION OF SEPHADEX BEADS

We have developed a method of induction of airway eosinophilia and neu trophilia in guinea pigs by intravenous injection of various types of Sephadex beads. In the first series of experiments, we have shown that G-50 Sephadex beads (Superfine, 24 mg/kg in conscious animals) induce d a large accumulation of inflammatory cells in alveolar walls. The br onchoalveolar lavage (BAL) fluid from animals treated with this dose o f Sephadex beads contained about 85 X 10(6) cells as compared to 20 X 10(6) cells in control animals. The eosinophils corresponded to 41% of the BAL cell population as assessed with Wright-Giemsa staining. Howe ver, in the BAL fluid from these bead-treated animals, a significant i ncrease of monocytes, lymphocytes, and neutrophils was also observed. We have also tested the potency of G-75, G-100, and G-200 Sephadex bea ds (Superfine) to induce eosinophilia in guinea pig. Nonlethal intrave nous doses of G-75 (14.27 mg/kg), G-100 (8.0 mg/kg), and G-200 (10.71 mg/kg) Sephadex beads were selected and induced variable levels of air way eosinophilia and neutrophilia in conscious guinea pigs. The percen tage of eosinophil recovered in the BAL fluid corresponded to 35, 61, and 44% of total cells for G-75, G-100, and G-200, respectively. The n eutrophils corresponded to 24, 2, and 12% of the total BAL cells for G -75, G-100, and G-200, respectively. Since the size of the beads did n ot seem to correlate with the intensity of airway eosinophilia and neu trophilia, the effect of lower doses of the G-50 Sephadex beads (9.86- 0.43 mg/kg) on the inflammatory cell infiltration was also tested. Res ults showed that there was a correlation between the neutrophil number and the number of beads (r = 0.996), whereas the number of eosinophil s was less directly correlated to the bead number (r = 0.812). The alv eolar eosinophils were purified from BAL fluid by centrifugation on a continuous Percoll gradient (65%) to separate eosinophils from neutrop hils. Normodense eosinophils (density 1.087-1.100 g/ml) obtained from Sephadex-treated animals were found at the bottom of the continuous Pe rcoll gradient (25 X 10(6); 98% purity). These highly purified eosinop hils released thromboxane A2 (TxA2) following stimulation with 2 muM i onophore A23187. The method of accumulation and purification of guinea pig alveolar eosinophils is simple, rapid, and provides a large numbe r of pure normodense cells for further biological studies. The inducti on of airway eosinophilia and neutrophilia in guinea pigs following in jection of various types of Sephadex beads could also provide an inter esting model for the study of the mechanisms of eosinophilia and neutr ophilia and their relationship to airway hyperresponsiveness.