Page 1151 - Veterinary Immunology, 10th Edition

Fourth, cancer/testis (CT) antigens are a group of tumor antigens
VetBooks.ir only expressed in the testes and in various malignancies. Their

function is unknown.
Fifth, tumors caused by viruses may express antigens

characteristic of the inducing virus. These antigens, although coded
for by a viral genome, are not part of a virion. Examples include the
FOCMA antigens found on the neoplastic lymphoid cells of cats
infected with feline leukemia virus and Marek's cancer-specific

antigens found on Marek's disease tumor cells in chickens. (Both of
these are virus-induced, naturally occurring, T cell tumors.)
Studies on these mutations and the neoantigens they generate
suggest that they are not widely shared but are tumor specific. They

depend on the genome of an individual tumor. Their production
also differs between tumor types. Thus neoantigen expression is
very high in melanomas and lung, stomach, and colorectal tumors,
and low in many leukemias. The vast majority of mutations do not

generate antigens that can be recognized by T cells.

Inflammation and Tumors

The tumor microenvironment often determines the development
and fate of cancer cells. The cancer cells communicate with nearby

cells, especially fibroblasts and inflammatory cells. As a result, the
elimination of cancer cells by immune mechanisms is determined in
part by the presence of inflammation. Chronic inflammatory

diseases increase the risk for developing many types of cancer;
conversely, the use of nonsteroidal antiinflammatory drugs reduces
tumor susceptibility (Fig. 35.2).

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