Sustained exposure to papain or H polygyrus extract induces splenic and peripheral blood eosinophilia. (A) Spleens and (B) blood from treated and untreated adult gata2:eGFP⁺ zebrafish were analyzed for gata2^hi leukocyte levels by FACS. Treated groups were injected weekly with papain or HpAg emulsified in IFA and tissues collected after one or 4 weeks. Control animals were either mock treated or uninjected. Bars represent means. *P < .05. **P < .001. Blood smears from fish immunized for 4 weeks with papain (C) or HpAg (D) showed elevated frequencies of PAS⁺ eosinophils. Images in panels C and D were acquired on an Olympus DP70 microscope with a 100× oil objective stained with PAS and hematoxylin. Images were collected with an Olympus DP Controller Version 2.1.1.183 and processed with Adobe Photoshop CS.