Isolation and characterization of immune complexes associated with malignant tumors and leprosy

We are dedicated to the study of circulating immune complexes (CIC) associated with different diseases: malignant tumors, leprosy and rheumatoid arthritis. Immune complexes were evaluated by various methods: 125I-Clq binding assay, 125I-IgG binding test, 125I-bovine conglutinin binding assay and polyethylene glycol precipitation test (3.5% and 2.5%). Techniques for the isolation and splitting of CIC in their components were performed in sera from patients with tumors and with leprosy. These methods consisted in the combination of CIC with protein A followed by elution with different buffers. CIC splitting techniques were first applied on immune complexes formed in vitro (BSA-aBSA, OVA-aOVA). The analysis of CIC fractions was done by SDS-PAGE, immunoelectrophoresis and immunoblotting techniques. Results were as follows: CIC levels correlated with active stages of disease, decreasing during remission so that CIC detection can be useful to evaluate response to treatment. The isolation and splitting of immune complexes into their components resulted in the obtention of immunologically active fractions, especially in sera from patients with gastrointestinal and breast cancer and with leprosy.