Immune complex-like materials in sera of patients with breast cancer: detection by complement-consumption assay

Sera of patients with breast cancer were tested for the presence of immune complexes by a complement-consumption assay. To increase the concentration of immune complexes and thus improve the chances of their detection, sera were first ultracentrifuged and the sedimented material was assayed. Sera were considered to be positive if they consumed at least 75% of the hemolytic activity under the conditions of the test. Of the 60 patients tested, 45% were positive as compared with 13.5% positive sera among health blood bank donors. The presence of immune complexes could not be correlated with the extent of disease, the age of the patients, treatment or lack of treatment at the time of the test, or the time that had elapsed since diagnosis. In a few control tests, treatment of samples with DNase had no effect on their anticomplementary activity, whereas reduction with 2-mercaptoethanol abrogated the activity. These results strengthened the assumption that the substances binding complement were indeed immune complexes.