[Non-specific changes in the complement system in neoplastic processes].
The study using immunochemical and biological methods was concerned with assaying complement components C1q, C3, C4, and C5, C3 derivatives--C3a and, C3(H2O), C1ing control protein, hemolytic activity (CH50), total proteolytic activity and regulatory immune complexes in sera from patients with cancer of the stomach, breast and ovary, subjects at risk of cancer and healthy donors. Neoplasia was associated with lowered levels of intact C3 and C1ing matched by high concentrations of C3a, C1q and C4. Hemolytic activity (CH50) was increased against the background of relatively higher total proteolytic activity both in healthy subjects and cancer patients. Significant decrease in C1ing concentration may be used as an additional biochemical prognosticator in breast cancer.