Various Candida and Torulopsis species differ in their ability to induce the production of C3, factor B and granulocyte-macrophage colony-stimulating factor (GM-CSF) in human monocyte cultures.

The incidence of infections with Candida albicans and also with non-albicans yeast species is increasing rapidly, particularly in immunocompromised patients. Eight Candida and Torulopsis species were compared for their ability to stimulate production of complement components C3 and factor B by monocytes. In addition, the release of granulocyte-macrophage colony-stimulating factor (GM-CSF) was determined, because this cytokine affects monocyte complement production. The highest ranked pathogenic yeasts, i.e., C. albicans, C. tropicalis and C. parapsilosis, were the most effective inducers of C3, factor B and GM-CSF production. C. krusei and T. glabrata showed intermediate activity, whereas C. kefyr, C. guilliermondii and T. candida had only a moderate stimulatory effect on C3 production and did not affect either factor B or GM-CSF release. The stimulated cytokine and complement production in response to the yeasts was highly variable in monocytes from different donors, but there was a consistent inverse relationship between C3 and GM-CSF concentrations in the monocyte supernates. This is in agreement with the previously described suppressive effect of GM-CSF on yeast-induced C3, but not factor B production. The monocyte responses elicited by a specific yeast species may be linked to its pathogenicity, and may also explain the predilection of some yeasts for particular underlying diseases.