Page 159 - Veterinary Immunology, 10th Edition

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FIG. 6.1 The location of the major populations of cells of the
mononuclear phagocyte system.

Structure

In suspension, monocytes are round cells about 15 to 20 µm in
diameter. They possess abundant cytoplasm, at the center of which
is a single large rounded nucleus (Fig. 6.2). Their central cytoplasm

contains mitochondria, large numbers of lysosomes, some rough
endoplasmic reticulum, and a Golgi apparatus, indicating that they
can synthesize and secrete proteins (Figs. 6.3 and 6.4). In living
cells, the peripheral cytoplasm is in continuous movement, forming

and reforming veil-like ruffles. Many macrophages show variations
in this basic structure. For example, blood monocytes have round
nuclei that elongate as the cells mature. Alveolar macrophages
contain very little rough endoplasmic reticulum, but their cytosol is

full of granules. The microglia of the central nervous system have
rod-shaped nuclei and very long cytoplasmic processes (dendrites)
that are lost when the cell responds to tissue damage.

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