Effects of Chronic Pulmonary Irradiation on Peripheral Lymphocytes and Their Function in the Dog

Abstract

Beagle dogs were exposed by inhalation to /sup 144/Ce in fused aluminosilicate particles, a relatively insoluble, inert carrier material. The radioactive particles deposited in the deep lung resulted in chronic irradiation of the pulmonary and adjacent thoracic tissues. Dogs exposed to high levels of /sup 144/Ce in fused aluminosilicate particles received more than 25,000 rad to lung by 3 yr after exposure. They developed a severe and persistent lymphopenia, and their remaining peripheral lymphocytes showed a decreased ability to respond to plant mitogens in vitro. The lymphopenia and the functional defect in the remaining lymphocytes suggested that an immunologic suppression existed in these dogs. Many lymphocytes were being killed in vivo by the radiation but another population was present that was viable in vivo but died when placed in vitro, accounting for at least part of the reduction in response to plant mitogens. No plasma factor was found that could account for the reduced lymphocyte transformation. The /sup 144/Ce-exposed dogs developed a high incidence of primary pulmonary hemangiosarcomas between 1 and 5 yr after exposure. This suggests that carcinogenesis after intrapulmonary deposition of radionuclides may result from a combination of the direct carcinogenic effect and the immunosuppressive effect of themore » irradiation.« less