Immunoglobulin complexes in sera of patients with malignancy

Sera frour 146 patients with malignancy, 59 normal controls and 42 patients hospitalized with non-malignant diseases were examined by a precipitin test with monoclonal rheumatoid factor (mRF) for the presence of circulating immune complexes containing IgG. Forty-two (29%) of the sera from cancer patients but only two of the sera from patients in each of the control groups contained such material. Similar results were obtained with a radioimmunoassay for immune complexes based on the same mRF. Sera from 23 of 65 patients with metastatic malignancy (35%) had elevated levels of immune complexes by this latter test. The presence of the material was not related to the source of malignancy, presence of carcinoembryonic or hepatitis antigens or of such autoantibodies as rheumatoid factor or anti-DNA. By density gradient ultracentrifugation the reacting material was identified as being of molecular size 19s or greater. It has not yet been further characterized with regard to the nature of any antigens present.