Page 1057 - Veterinary Immunology, 10th Edition

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FIG. 32.2 Some of the mechanisms involved in the pathogenesis
of the Arthus reaction.

Although it has long been assumed that immunoglobulins do not
themselves damage antigens, evidence has shown that they can kill
microorganisms and cause tissue damage. When provided with

singlet oxygen from phagocytic neutrophils, antibodies can catalyze
the production of oxidants such as ozone. This ozone kills not only
bacteria but also nearby cells.
Neutrophil proteases also act on C5 to generate C5a, which

promotes further neutrophil accumulation and degranulation.
Other enzymes released by neutrophils make mast cells
degranulate or generate kinins. As a result of all this, inflammation
and destruction of blood vessel walls cause edema, vasculitis, and

hemorrhage characteristic of an Arthus reaction.
Although the classical direct Arthus reaction is produced by local
administration of an antigen to hyperimmunized animals, any
technique that generates immune complexes in tissues will

stimulate a similar response. A reversed Arthus reaction can
therefore be produced if antibodies are administered intradermally
to an animal with a high level of circulating antigen. Injected,
preformed immune complexes, particularly those containing a

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