Phagocytosis

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Answers to Case 04 1. The cell in the image is a neutrophil (PMN leukocyte) and it illustrates the process of phagocytosis. The neutrophil (indicated by black arrow) in the image to the right has phagocytosed bacterial microorganisms (thin red arrows) into its cytoplasm. Phagocytosis is an important part of the innate immune system; macrophages and neutrophils are capable of phagocytosis. The image below also illustrates phagocytosis; the phagocytic cells in the lower image are mostly macrophages that have ingested bacterial microorganisms. Phagocytosis involves the ingestion and digestion of a variety of materials encountered in the extracellular environment including microorganisms, insoluble foreign particles (e.g. suture material, wood splinters, etc), damaged or dead host cells, and cell debris. Return to Questions

Phagocytosis of bacterial microorganisms (blue rods) by a macrophage (arrow) 2. There are several stages of phagocytosis: Chemotaxis - directed, purposeful movement of cells up a gradient of chemotactic factors. It is an energy-dependent process. The most important chemotacic factors for PMN's are the C5a fragment of complement, bacterial products (e.g. LPS), leukotriene B4, and certain chemokines (e.g. IL-8) Attachment of the bacterium or foreign material to