Page 1197 - Veterinary Immunology, 10th Edition

in controlling these diseases.
VetBooks.ir Bystander Activation

When viruses destroy cells, previously hidden antigens may be
released. These may activate nearby lymphocytes that had not been

involved in the antiviral response. Additionally, T cells might, in
responding to an antigen, produce a mixture of cytokines such as
the tumor necrosis factors and nitric oxide, that can kill nearby cells
and trigger an autoimmune response. Viruses may induce an
inflammatory response that results in the release of multiple

cytokines. Pathogens may trigger inappropriate lymphocyte
proliferation by acting through pattern-recognition receptors to
generate co-stimulatory molecules and proinflammatory mediators.

These cytokines may activate previously dormant T cells. As a
result, the T cells may attack autoantigens that they previously
ignored. Evidence suggests that Coxsackie virus–induced diabetes
mellitus is mediated in large part through bystander activation (Fig.
36.3). Prolonged infection with some viruses may induce

autoimmunity as a result of chronic activation of the immune
responses. Thus a prolonged polyclonal B cell activation may result
in the eventual emergence of autoreactive clones.

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