Page 145 - Veterinary Immunology, 10th Edition

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FIG. 5.12 NETs formed by bovine neutrophils cocultured with
sporozoites of the protozoan parasite, Eimeria bovis. A, Several
sporozoites can be seen sticking to a network of fibers originating
from dead and disrupted neutrophils (scale bar, 50 µm). B, At
higher magnification, it can be seen that the NETs consist of a
meshwork of filaments, many of which are attached to a sporozoite
(scale bar, 5 µm). (From Behrendt JH, Ruiz A, Zahner H, et al: Neutrophil
extracellular trap formation as innate immune reactions against the apicomplexan
parasite Eimeria bovis, Vet Immunol Immunopathol 133:1-8, 2010.)

Ingestion

As a neutrophil crawls toward a chemotactic source, a lamellipod
advances first, followed by the main portion of the cell. The cytosol

of the lamellipod contains a filamentous network of actin and
myosin, whose state determines the fluidity of the cytoplasm. When
a neutrophil meets a bacterium, the lamellipod flows over and

around the organism, and binding occurs between opsonins on the
organism and receptors on the neutrophil surface (Fig. 5.13). When
antibody-coated microbes are bound by neutrophil CD32, they
trigger polymerization of actin. As a result, actin-rich lamellipods
extend from the cell to engulf the particle (type 1 phagocytosis).

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