Differential responses of mouse and human eosinophils to stimuli. Panels A and B show superoxide production induced by immobilized IgGs, PAF, IL-5 or eotaxin in human and IL-5 transgenic mouse eosinophils, respectively. Human eosinophils were stimulated with immobilized IgGs [wells precoated with 100 µg/ml human (h)IgG1, mouse (m)IgG1, mIgG2a or mIgG2b], 1 µM PAF, 5 ng/ml recombinant hIL-5, 50 ng/ml hEotaxin, or 10 ng/ml PMA. Peritoneal lavage mouse eosinophils were stimulated similarly except recombinant mIL-5 and mEotaxin were used at the same concentrations. Superoxide production was measured by reduction of cytochrome c. Results are means ± SEM of three experiments. Panels C and D depict the morphology of human and mouse eosinophils stimulated with immobilized hIgG1 and mIgG2a, respectively. Original magnification; ×400.