MECHANISMS OF PHAGOCYTOSIS IN MACROPHAGES

• Published in: Annual review of immunology Vol. 17; no. 1; pp. 593 - 623
• Main Authors: Aderem, Alan, Underhill, David M
• Format: Journal Article
• Language: English
• Published: Palo Alto, CA 94303-0139 Annual Reviews 01.01.1999; 4139 El Camino Way, P.O. Box 10139 Annual Reviews, Inc; USA
• Subjects: Animals; apoptosis; Apoptosis - immunology; Caenorhabditis elegans - genetics; Caenorhabditis elegans - immunology; cytoskeleton; Humans; Legionella pneumophila - immunology; Lipopolysaccharide Receptors - metabolism; Macrophages - immunology; membrane traffic; Mycobacterium tuberculosis - immunology; pathogens; Phagocytosis - immunology; receptors; Receptors, Complement - metabolism; Receptors, IgG - metabolism; Receptors, Immunologic - immunology; Receptors, Scavenger; Receptors, Vitronectin - metabolism; Salmonella typhimurium - immunology; signal transduction; Vacuoles - immunology
• ISSN: 0732-0582; 1545-3278
• DOI: 10.1146/annurev.immunol.17.1.593

Phagocytosis of pathogens by macrophages initiates the innate immune response, which in turn orchestrates the adaptive response. In order to discriminate between infectious agents and self, macrophages have evolved a restricted number of phagocytic receptors, like the mannose receptor, that recognize conserved motifs on pathogens. Pathogens are also phagocytosed by complement receptors after relatively nonspecific opsonization with complement and by Fc receptors after specific opsonization with antibodies. All these receptors induce rearrangements in the actin cytoskeleton that lead to the internalization of the particle. However, important differences in the molecular mechanisms underlying phagocytosis by different receptors are now being appreciated. These include differences in the cytoskeletal elements that mediate ingestion, differences in vacuole maturation, and differences in inflammatory responses. Infectious agents, such as M. tuberculosis , Legionella pneumophila , and Salmonella typhimurium , enter macrophages via heterogeneous pathways and modify vacuolar maturation in a manner that favors their survival. Macrophages also play an important role in the recognition and clearance of apoptotic cells; a notable feature of this process is the absence of an inflammatory response.