Circulating immune complexes in sera of dogs with benign and malignant breast disease.

The Raji cell radioimmunoassay was adapted to measure circulating immune complexes (CIC's) in the sera of 74 dogs with benign and malignant breast disease. In dogs with recently diagnosed spontaneous breast cancer, 57% (29 of 51) had elevated CIC's, with some levels as high as those found in the sera of dogs with systemic lupus erythematosus. The sera of 10 of 23 dogs with benign breast disease also demonstrated elevated levels of CIC's. Two weeks following mastectomy, repeat CIC levels were obtained in 30 dogs. Elevated CIC levels returned to normal in all dogs with benign breast disease but in only 33% of dogs with breast cancer. Dogs with persistent elevation of CIC's were at greater risk of developing metastatic breast cancer. Serum total hemolytic complement was significantly higher (p < 0.05) in dogs with untreated breast cancer than in healthy dogs but did not correlate with the level of CIC's found. Two weeks after mastectomy, total hemolytic complement levels had returned to normal. By sucrose density gradient ultracentrifugation, the complexes were shown to sediment at 19 S. These studies indicate that the dog may be a good model for elucidating the significance of elevated CIC's in breast cancer.