Page 1182 - Veterinary Immunology, 10th Edition
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in old dogs. Eighty percent are CD8 , whereas the remainder are
VetBooks.ir double-negative. Most (70%) have γ/δ TCRs, especially if the tumor
is confined to the epidermis.
Avian Lymphoid Tumors
Marek's disease herpesvirus induces T cell tumors and severe
immunosuppression in chickens. Birds with this disease are usually
immunosuppressed. Thus their antibody responses, rejection of
allografts, and delayed hypersensitivity responses are all depressed.
This depression results from several factors, including virus-
induced lymphoid destruction and the development of suppressor
macrophages. These macrophages restrict the replication of the
tumor cells, but in doing so they suppress the resistance of birds to
other infections. Late immunosuppression can occur in the absence
of tumors. Lymphoid leukosis is a tumor of B cell origin. Affected
birds normally have a depressed antibody response and reduced
responses to mitogens. Nevertheless, some cases of this disease may
present with hypergammaglobulinemia.
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