Neutrophils and Macrophages

Roles and functions of neutrophils and monocytes/macrophages in host defense

• Neutrophils and monocytes are circulating phagocytes that recognize and ingest microbes for intracellular killing.
• Neutrophils are the most abundant leukocytes in the blood, numbering 4,000 to 10,000 per μL, and are stimulated to proliferate by cytokines called colony-stimulating factors (CSFs).
• Neutrophils are the first and most numerous cell type to respond to most infections, particularly bacterial and fungal infections, and dominate acute inflammation.
• Neutrophils express receptors for products of complement activation and antibodies, which enhance phagocytosis and transduce activating signals to enhance their ability to kill ingested microbes.
• Neutrophils are also recruited to sites of tissue damage in the absence of infection, where they initiate the clearance of cell debris.
• Monocytes are less abundant in the blood than neutrophils, numbering 500 to 1000 per μL, and differentiate into macrophages in extravascular tissues during inflammatory reactions.
• Macrophages survive in tissues for long periods and serve several important roles in host defense, including ingesting and destroying microbes, clearing dead tissues, initiating tissue repair, and producing cytokines that induce and regulate inflammation.
• Macrophages express various receptor families involved in their activation and functions, including pattern recognition receptors, phagocytic receptors, and cytokine receptors.
• Macrophages may be activated by two different pathways - classical and alternative - that serve distinct functions: classical macrophages are involved in destroying microbes and triggering inflammation, while alternative macrophages are important for tissue repair and terminating inflammation.
• The relative abundance of these two forms of activated macrophages may influence the outcome of host reactions and contribute to various disorders.
• Although our discussion has been limited to the role of phagocytes in innate immunity, macrophages are also important effector cells in both the cell-mediated arm and the humoral arm of adaptive immunity, respectively.
• Neutrophils and monocytes/macrophages play crucial roles in host defense by recognizing and ingesting microbes, initiating inflammation and tissue repair, and producing cytokines that regulate immune responses.

Test your knowledge on the roles and functions of neutrophils and monocytes/macrophages in host defense with this informative quiz. Learn about the important roles these phagocytes play in recognizing and ingesting microbes, triggering inflammation, and initiating tissue repair. Explore the different receptor families involved in their activation and functions, and delve into the distinct functions of classical and alternative macrophages. See how well you understand the crucial roles of these cells in innate immunity and their contributions to various disorders. Take this