RT Book, Section A1 Douglas, Steven D. A1 Douglas, Anne G. A2 Kaushansky, Kenneth A2 Prchal, Josef T. A2 Burns, Linda J. A2 Lichtman, Marshall A. A2 Levi, Marcel A2 Linch, David C. SR Print(0) ID 1180445349 T1 Structure, Receptors, and Functions of Monocytes and Macrophages T2 Williams Hematology, 10e YR 2021 FD 2021 PB McGraw-Hill Education PP New York, NY SN 9781260464122 LK hemonc.mhmedical.com/content.aspx?aid=1180445349 RD 2024/03/28 AB SUMMARYThe monocyte is a spherical cell with prominent surface ruffles and blebs when examined by scanning electron microscopy. As the monocyte enters the tissue and differentiates into a macrophage, the cell volume and number of cytoplasmic granules increase. Cell shape varies, depending on the tissue in which the macrophage resides (eg, lymph node, lung, liver spleen, brain). A characteristic feature of macrophages is their prominent electron-dense membrane-bound lysosomes, which fuse with phagosomes to form secondary lysosomes. The latter contain ingested cellular and noncellular material in different stages of degradation. A broad range of surface receptors for many ligands, including the Fc portion of immunoglobulin, complement proteins, cytokines, chemokines, lipoproteins, and others, are on the cell surface. Macrophages play a major role in innate as well as adaptive immunity. Macrophages differ in appearance, biochemistry, and function based on the environment in which they mature from embryonic cells or circulating monocytes. These differences are exemplified by the diversity among dendritic cells of lymph nodes, histiocytes of connective tissue, osteoclasts of bone, Kupffer cells of liver, microglia of the CNS, and macrophages of the serosal surfaces, each fashioned to meet the local needs of the mononuclear phagocyte system, which plays a role in inflammation and host defense against microbes. Modern cell biologic methods have advanced our knowledge of the surface proteins and mechanisms of endocytosis and lysosomal degradation of macrophages. These studies, in turn, have resulted in the discovery that dendritic cells are potent, highly specialized antigen-presenting cells. Subsequent development of monoclonal antibodies and molecular cloning of surface proteins and cytokines, followed by microarray analysis and single cell omics, provided the sensitive and specific tools which enabled the analysis of monocyte/macrophage functions in vitro and in vivo, bringing important insights into their cytotoxic and antimicrobial activities and their tropic and homeostatic functions.