Eosinophils have decreased early apoptosis and increased viability in acidic pH. Murine (A-C) and human eosinophils (D-F) were incubated in media buffered to various pH. Viability analysis shows that incubation of murine eosinophils in acidic media for 4 hours affects number of viable eosinophils (A) and number of early apoptotic murine eosinophils (B). Viability analysis of murine eosinophils over a 7-hour time course shows that incubation of murine eosinophils in acidic media affects percentage of viable eosinophils (C). Representative flow cytometric analysis of human eosinophils incubated at various pH for 24 hours (D) with quantification showing average percentage of viable eosinophils with SD (E). Human eosinophils were incubated in media buffered to pH 7.5 and 6.0 in the presence of indicated doses of IL-5 for 18 hours (F). Results show the average ± SD of triplicate incubations. *P < .05. Representative experiment (of > 11 and 3) is shown for murine and human eosinophils, respectively.