Page 1150 - Veterinary Immunology, 10th Edition

progress of the tumor.
VetBooks.ir example, melanoma cells may express the products of mutated
Second, there are mutated forms of normal cellular proteins. For

oncogenes on their surface (Fig. 35.1). Some tumor antigens are

recognized because they are abnormally glycosylated. Chemically
induced tumors may express surface antigens unique to the tumor
and not to the inducing chemical. Because carcinogenic chemicals
can produce many different mutations, tumors induced by a single

chemical in different animals may be antigenically different. Even
within a single chemically induced tumor mass, distinct
subpopulations of cells exist. As a result, immunity to one
chemically induced tumor does not prevent growth of a second

tumor caused by the same chemical.

FIG. 35.1 Some of the great variety of new antigens that may
appear on the surface of tumor cells and provoke an immune
response.

Third, normal proteins are produced in excessive amounts. A
good example is the production of prostate-specific antigen (PSA)
by prostate carcinomas of humans. PSA is exclusively produced by
the prostate epithelium. Increased blood levels of this protein

indicate excessive prostate activity. One cause of this is the growth
of a carcinoma.

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