Page 1377 - Veterinary Immunology, 10th Edition

activation and mitosis. Under the influence of thiopurine
VetBooks.ir methyltransferase, it is converted in the liver to 6-mercaptopurine,

which inhibits both DNA and RNA synthesis. T and B cells are
especially susceptible to this effect. It can suppress both primary

and secondary antibody responses if given after antigen exposure.
Azathioprine has significant antiinflammatory activity since it
inhibits the production of macrophages. It has no effect on the
production of cytokines or immunoglobulins by lymphocytes but

tends to suppress T cell–mediated responses to a greater extent than
B cell responses. Its major toxic effects include bone marrow
depression (affecting leukocytes rather than platelets or red cells),
acute pancreatitis, and gastroenteritis. Azathioprine is useful in the

control of allograft rejection. It is favored by many clinicians for the
treatment of immune-mediated skin diseases because of its
combination of antiinflammatory and immunosuppressive activity.
It is commonly used in association with corticosteroids. If

azathioprine is used in dogs, marrow function should be monitored
and the dose adjusted if necessary. There are breed-related
variations in azathioprine metabolism in dogs that may affect its
effectiveness and toxicity.

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