Page 1119 - Veterinary Immunology, 10th Edition

The allograft rejection process is directed against the dominant
VetBooks.ir antigens on the cells of the graft. The MHC molecules tend to

trigger a T cell–mediated rejection response, whereas the blood
group antigens tend to trigger antibody formation. The rejection

process may be divided into two phases. First, the host's
lymphocytes encounter the antigens of the graft and trigger a
response. Second, cytotoxic T cells and antibodies from the host
enter the graft and destroy graft cells (Fig. 34.4).

FIG. 34.4 Some of the mechanisms involved in the rejection of an
allograft (see text for details).

Innate Mechanisms

Damage to the graft as a result of surgical trauma and ischemia

followed by reperfusion upregulates MHC expression and
generates cytokines and inflammatory mediators that attract
neutrophils and macrophages into the graft. If large quantities of

damage-associated molecular patterns (DAMPs) such as high
mobility group box protein-1 (HMGB1) are generated, they will
activate toll-like receptors and other pattern-recognition receptors.
An increase in expression of the stress protein MIC-A on graft

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