Differences in oxidant release by human polymorphonuclear leukocytes produced by stimulation with different phases of coccidioides immitis

Human polymorphonuclear leukocytes (PMNL) inhibit growth of arthroconidia and young spherules but not mature spherules of Coccidioides immitis. To evaluate these differences, oxidants were measured when PMNL were exposed to C. immitis or other particulate stimuli. Concentrations of arthroconidia, young spherules, mature spherules, and Candida glabrata were adjusted to result in equivalent superoxide release. Hydrogen peroxide and hypochlorous acid were stimulated by arthroconidia or young spherules but were undetectable after exposure to mature spherules. Levels of catalase in mature spherules were too low to account for the low levels of hydrogen peroxide and hypochlorous acid. When mature spherules were added to arthroconidia or zymosan, stimulation of hydrogen peroxide and hypochlorous acid occurred. The results suggest that mature spherules stimulate superoxide release but interfere with hydrogen peroxide and hypochlorous acid production. The low levels of these antimicrobial oxidants may contribute to resistance of C. immitis to human PMNL.