UCLA Conference. Monocytes and macrophages: functions and diseases.

The mononuclear phagocyte complex is a widespread system of cells originating in the bone marrow monoblast and promonocyte, passing through the intermediate monocyte stage in the blood, and culminating in the tissue macrophages of the lung, liver, spleen, and pleural and peritoneal spaces. The cells are prominently phagocytic and have a well-developed lysosomal system. They function in host defense reactions against micro-organisms, in interactions with lymphoid cells in immunity, in disposal of cell debris, and possible in the regulation of granulopoiesis. Monocytes and the alveolar macrophage are the most accessible cells of this system for study. Several diseases of mononuclear phagocytes have been identified and characterized. These include microbicidal defects associated with increased susceptibility to infection, enzyme defects leading to storage diseases, and neoplastic diseases in which both cell proliferation and biologically active cell products contribute to the clinical disorder.