Candidacidal activity of monocyte-derived human macrophages: relationship between Candida killing and oxygen radical generation by human macrophages.

Freshly isolated human monocytes ingested and killed Candida albicans, and generated O2- H2O2 and .OH efficiently. When monocytes were cultured in vitro, these cells transformed into macrophages. Cultured monocytes retained their ingestive activity but lost their candidacidal activity almost completely after day 3. The release of O2- by monocytes decreased slightly with culture and that of .OH was markedly decreased on day 3 of culture. The activity of myeloperoxidase in the monocytes decreased with culture. These results suggested that the loss of candidacidal activity is due to the decrease of .OH generation and myeloperoxidase activity in cultured monocytes.