Detection in the blood serum of breast cancer patients of circulating immune complexes containing antigens showing common epitopes with structural proteins of mouse mammary tumour virus (MMTV).

In the blood serum of a proportion of breast cancer patients (29.4%) immune complexes specifically reacting with the immunoglobulins of the serum against MMTV structural proteins were detected using indirect enzyme-linked immunosorbent assay (ELISA). The presence of such complexes could decrease the titre of antibodies reactive with MMTV in the blood serum of breast cancer patients.