Phagocytosis: at the crossroads of innate and adaptive immunity.
Phagocytosis, the process by which cells engulf large particles, requires a substantial contribution of membranes. Recent studies have revealed that intracellular compartments, including endocytic organelles and the endoplasmic reticulum (ER), can engage in fusion events with the plasma membrane at the sites of nascent phagosomes. The finding that ER proteins are delivered to phagosomes, where degraded peptides are loaded onto major histocompatibility complex (MHC) class II molecules, has significantly enhanced our understanding of the immune functions associated with these organelles. Although it is well known that pathogens are killed in phagosomes, the contribution of ER proteins to phagosomes has provided a novel pathway for the loading of exogenous peptides onto MHC class I molecules, a process known as cross-presentation. Thus, phagocytosis has evolved from a nutritional function in unicellular organisms to play key roles in both innate and adaptive immunity in vertebrates.
Jutras
Isabelle
I
Département de pathologie et biologie cellulaire, Université de Montréal, Montréal, Quebec H3C 3J7, Canada. isabelle.jutras@umontreal.ca
Desjardins
Michel
M
D000818:Animals; D017951:Antigen Presentation / Q000276:immunology; D000941:Antigens / Q000276:immunology / Q000378:metabolism; D007110:Immunity, Active; D007113:Immunity, Innate; D008954:Models, Biological; D018448:Models, Immunological; D010587:Phagocytosis / Q000276:immunology*; D010588:Phagosomes / Q000276:immunology / Q000378:metabolism
D000941:Antigens