Patterns, Receptors, and Signals: Regulation of Phagosome Maturation

Recognition of microbial pathogens and dead cells and their phagocytic uptake by specialized immune cells are essential to maintain host homeostasis. Phagosomes undergo fusion and fission events with endosomal and lysosomal compartments, a process called ‘phagosome maturation’, which leads to the degradation of the phagosomal content. However, many phagocytic cells also act as antigen-presenting cells and must balance degradation and peptide preservation. Emerging evidence indicates that receptor engagement by phagosomal cargo, as well as inflammatory mediators and cellular activation affect many aspects of phagosome maturation. Unsurprisingly, pathogens have developed strategies to hijack this machinery, thereby interfering with host immunity. Here, we highlight progress in this field, summarize findings on the impact of immune signals, and discuss consequences for pathogen elimination.