Fagolisosomas

Fagolisosomas, also known as phagolysosomes, are intracellular compartments formed when a phagosome fuses with a lysosome in phagocytic cells such as macrophages, neutrophils, and dendritic cells. They contain hydrolytic enzymes and an acidic environment that work together to degrade ingested particles, including bacteria, fungi, and dead or damaged cells.

The formation and maturation of fagolisosomas involve a series of coordinated steps. After phagocytosis, the phagosome acquires markers of early endosomes and undergoes maturation, moving through late endosomal stages. Rab GTPases, phosphoinositides, and SNARE proteins regulate fusion with lysosomes. The lumen becomes increasingly acidic via vacuolar-type ATPases, and lysosomal hydrolases are delivered to the phagosome. The resulting phagolysosome is equipped to digest its contents through proteases, lipases, nucleases, and other enzymes, and it can generate reactive oxygen and nitrogen species to help kill ingested microbes.

Functions of fagolisosomas include degradation of internalized pathogens and debris, processing of antigens for presentation on MHC class II molecules, and contributing to antimicrobial defense. In addition to digestion, the phagolysosomal environment supports antigen processing that shapes adaptive immune responses, particularly in dendritic cells and macrophages.

Clinical relevance includes the role of fagolisosomes in innate immunity and host defense. Some pathogens, such as Mycobacterium tuberculosis, can evade or disrupt phagolysosome maturation to survive intracellularly. Disorders affecting phagolysosome formation or function, including certain lysosomal trafficking defects, can predispose individuals to recurrent infections and immune dysfunction.