Making peace with the beast within

Abstract

Immunology One way that immune cells such as neutrophils and macrophages contribute to host defense is by engulfing microbes. This process, known as phagocytosis, typically entails the formation of an organelle around the microbes called the phagosome, which then fuses with lysosomes to facilitate degradation. However, some pathogens can survive and even thrive within phagosomes. Westman et al. investigated the process by which phagosomes sequester and control the rapidly growing fungus Candida albicans after phagocytosis. The macrophage phagosome expands to match the fungus' growth through the calcium-dependent insertion of lysosomes. If lysosomal fusion is inhibited, the phagosomes rupture, leading to NLRP3 inflammasome activation, host cell death, and the enhanced growth and escape of C. albicans . However, by tolerating the burgeoning fungus, lysosomal fusion appears to contain infection and give the host precious time to mount its defenses. Cell Host Microbe 10.1016/j.chom.2020.09.004 (2020).