Page 565 - Veterinary Immunology, 10th Edition

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FIG. 18.11 The four major pathways by which the cells of the
immune system can kill nucleated target cells. These targets would
normally be tumor cells or virus-infected cells. T cells and NK cells
are directly cytotoxic. Macrophages secrete NOS and enzymes that
kill nearby cells. Cells with Fc receptors act through ADCC
mechanisms.

Whether a macrophage participates in ADCC depends on its Fc
receptors and its degree of activation. Macrophage-activating
cytokines such as IFN-γ or granulocyte-macrophage colony-
stimulating factor (GM-CSF) promote ADCC. Macrophages may
also destroy target cells in an antibody-independent process. For

example, when they ingest bacteria or parasites, macrophages
release nitric oxide, proteases, and TNF-α. The nitric oxide will kill

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