Influence of Fungal Surface Components on the Interaction of Coccidioides immitis with Polymorphonuclear Neutrophils

Polymorphonuclear neutrophils (PMNs) possess phagocytic and fungicidal activity against Coccidioides immitis that declines during maturation from arthroconidia to round cells, is lost throughout spherule maturation, and returns when endospores are released from ruptured spherules. Studies of PMN chemiluminescence, iodination, and degranulation give similar results. Phagocytosis of forms other than spherules is strain dependent and enhanced by immune serum. The absence of adequate PMN-spherule interaction may be attributed to the production of an extracellular fibrillar matrix, glycoprotein in composition, that restricts intimate PMN-spherule contact. When the spherule ruptures, PMNs enter to phagocytose endospores that are themselves invested by a matrix derived from the inner spherule wall. The immunochemical relationship between the outer matrix and the inner matrix remains to be discovered. Nevertheless, presence of the outer matrix may help to explain the long-standing histopathologic observation that PMNs fail to attack spherules until they release their endospores.