Immunological activation of polymorphonuclear neutrophils for fungal killing: studies with murine cells and blastomyces dermatitidis in vitro.

The interaction of elicited murine polymorphonuclear neutrophils (PMN) and the thermally dimorphic fungal pathogen Blastomyces dermatitidis in vitro was studied. The PMN elicited intraperitoneally with thioglycollate, in normal mice or mice immune to B dermatitidis, failed to reduce colony forming units (CFU) of B dermatitidis in the inoculum in a 4-hr in vitro assay, even in the presence of 10% fresh immune serum. In contrast, PMN elicited intraperitoneally in immune mice by injection of nonviable B dermatitidis cells significantly reduced inoculum CFU (60 +/- 5%) under the same conditions. Furthermore, nonviable B dermatitidis intraperitoneally (i.p.) in normal mice or nonviable Candida albicans i.p. in immune mice failed to elicit peritoneal exudate cells that reduced inoculum CFU in this system. These results support the concept that PMN, elicited in a site by means of an immunological reaction, acquired enhanced microbicidal activity. The fungicidal activity of immunologically elicited PMN was shown to be most effective at high effector to target cell ratios (1,000:1), maximal within 2 hr of coculture, and significantly enhanced in the presence of fresh immune serum compared to heat-inactivated immune serum, normal mouse serum, or fetal bovine serum. Such PMN also had significantly enhanced fungicidal activity against C albicans compared to normal PMN. Fungicidal activity was abrogated in the presence of catalase, implicating hydrogen peroxide generation as the killing mechanism in the activated cells.