Induction of lung eosinophilia and neutrophilia in guinea pigs following injection of Sephadex beads

Abstract

We have developed a method of induction of airway eosinophilia and neutrophilia 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) induced a large accumulation of inflammatory cells in alveolar walls. The bronchoalveolar lavage (BAL) fluid from animals treated with this dose of Sephadex beads contained about 85 × 10⁶ cells as compared to 20 × 10⁶ cells in control animals. The eosinophils corresponded to 41% of the BAL cell population as assessed with Wright-Giemsa staining. However, in the BAL fluid from these bead-treated animals, a significant increase of monocytes, lymphocytes, and neutrophils was also observed. We have also tested the potency of G-75, G-100, and G-200 Sephadex beads (Superfine) to induce eosinophilia in guinea pig. Nonlethal intravenous 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 airway eosinophilia and neutrophilia in conscious guinea pigs. The percentage 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 neutrophils 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 not seem to correlate with the intensity of airway eosinophilia and neutrophilia, 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. Results showed that there was a correlation between the neutrophil number and the number of beads (r=0.996), whereas the number of eosinophils was less directly correlated to the bead number (r=0.812). The alveolar eosinophils were purified from BAL fluid by centrifugation on a continuous Percoll gradient (65%) to separate eosinophils from neutrophils. Normodense eosinophils (density 1.087–1.100 g/ml) obtained from Sephadex-treated animals were found at the bottom of the continuous Percoll gradient (25 x 10⁶; 98% purity). These highly purified eosinophils released thromboxane A₂ (TxA₂) following stimulation with 2μM ionophore A23187. The method of accumulation and purification of guinea pig alveolar eosinophils is simple, rapid, and provides a large number of pure normodense cells for further biological studies. The induction of airway eosinophilia and neutrophilia in guinea pigs following injection of various types of Sephadex beads could also provide an interesting model for the study of the mechanisms of eosinophilia and neutrophilia and their relationship to airway hyperresponsiveness.