Eosinophil chemotactic activity in bronchoalveolar lavage fluid obtained from Toxocara canis-infected rats

We examined eosinophil chemotactic activity (ECA) in bronchoalveolar lavage fluid (BALF) obtained from rats infected with Toxocara canis. For 4 weeks after infection, the number of eosinophils was determined in peripheral blood and BALF. ECA was assayed using a microchemotaxis chamber. Eosinophils in peripheral blood and BALF increased markedly after infection, peaking at 12 days and 2 weeks, respectively. ECA in BALF also increased significantly and peaked 2 weeks after infection. Partial characterization revealed that ECA was heat labile, lipid soluble, and resistant to trypsin digestion. Two ECA peaks were identified by molecular sieve column chromatography: one near the egg albumin marker (MW 45,000) and the other observed after elution with quinacrine (MW 472.9). Treatment with a specific leukotriene (LT) B4 receptor antagonist (ONO-4057), a platelet activating factor (PAF) receptor antagonist (TCV-309), and an anti-interleukin (IL)-5 monoclonal antibody (TB13) significantly reduced the ECA, suggesting that LTB4, PAF, and IL-5 contribute to the accumulation of eosinophils in the lungs of rats infected with T. canis.