Differential effect of Cryptococcus neoformans on the production of IL-12p40 and IL-10 by murine macrophages stimulated with lipopolysaccharide and gamma interferon

In the present study, we examined the in vitro effect of Cryptococcus neoformans on the production of interleukin-12 (IL-12) and IL-10 by murine macrophages. At a dose of 1x10⁵, 1x10⁶ or 1x10⁷ ml^-1, a highly virulent strain of C. neoformans (strain YC-11) suppressed the production of IL-12p40 by a murine macrophage cell line, J774.1 stimulated with lipopolysaccharide (LPS) and interferon (IFN)-γ, while the production of IL-10 was not inhibited, but rather slightly augmented. The suppression of IL-12p40 production did not change by neutralizing anti-IL-10 mAb. A direct contact of C. neoformans with macrophages was largely involved in this inhibitory effect, since placement of a 0.45 μm pore membrane between the organism and macrophages prevented such effect. On the other hand, the culture supernatant of YC-11 did not inhibit macrophage IL-12p40 production when used at a lower dose, which contained an equivalent amount of capsular polysaccharide to that in the supernatant of YC-11 cultured at 1x10⁵ or 1x10⁶ ml^-1, although it showed a small suppression at higher doses. Our results suggest that C. neoformans may suppress the induction of Th1 responses by inhibiting macrophage IL-12 production predominantly through a direct contact-dependent mechanism and to a lesser extent by a certain soluble factor(s) released from this microorganism. Copyright (C) 1999 Federation of European Microbiological Societies.