Inhibition of different phases of Coccidioides immitis by human neutrophils or hydrogen peroxide.

As arthroconidia of Coccidioides immitis transform into spherules, the fungal particles progressively become more resistant to the inhibitory effects of human polymorphonuclear leukocytes (PMNLs) as measured by PMNL inhibition of fungal incorporation of N-acetylglucosamine. Similar changes were noted when leucine incorporation was measured. When H2O2, at a concentration of 2.0 mM, was substituted for PMNLs, an equivalent inhibition of arthroconidia was produced and, as with PMNL effects, was lost with spherule maturation. The results from these studies indicate that C. immitis may evade natural inhibition by PMNLs by transformation into the spherule phase.