Intracellular cryptococci suppress Fc-mediated cyclin D1 elevation.

Cryptococcus neoformans (Cn) is the only encapsulated fungal pathogen pathogenic to humans and macrophages play a vital role in the Cn infection pathway. Previously we documented that phagocytosis or crosslinking of FcgammaR on macrophage cell surface promoted macrophage cell cycle progression via the activation of MAPK pathway. However, we seldom observed sustained macrophage growth after they phagocytosed live Cn. In fact, many macrophages were finally observed to undergo apoptotic changes after phagocytosis of live Cn. Here we report that cyclin D1 elevation in macrophages promoted by phagocytosis was suppressed by intracellular Cn cells. This suggests a novel cytotoxic mechanism for host cells of intracellular cryptococci.