Recovery of Immunologically Reactive Antibodies and Antigens from Breast Cancer Immune Complexes by Preparative Isoelectric Focusing

A new technique for the recovery of immunologically reactive antibodies and putative antigens from breast cancer-associated immune complexes was described. Soluble immune complexes were isolated from extracellular fluids by 2.5% polyethylene glycol fractionation and affinity chromatography on Protein A:Sepharose CL-4B. The immune complexes bound to immobilized Protein A were then subjected to preparative isoelectric focusing. The dissociated immunoglobulins and putative antigens were recovered from the appropriate pH regions of the preparative isoelectric focusing gel. G-type immunoglobulins recovered from immune complexes isolated from a breast cancer patient bound to the recovered putative antigen(s) and three breast cancer cell culture lines, but these immunoglobulins did not bind to carcinoembryonic antigen or other cancer cell culture lines originating in colon, pancreas, prostate, or lymphoblast. The recovered putative antigens had isoelectric points between pH 3.0 and 5.0 and molecular weights of 20,000 and 42,000.