Immune complexes of IgG1 and IgG3 subclasses in human breast cancer sera detected by monoclonal antibodies in an indirect immunoenzymatic assay.

Circulating immune complexes (CIC) of the IgG class were detected in sera from 37 (35.58%) out of 104 of the preoperated breast cancer patients studied using a CIq solid-phase enzymatic assay. Sera of positive patients were then tested to identify the IgG subclasses which are part of the complexes with the aim of showing a better correlation between CIC and disease evolution. IgG1- and IgG3-CIC were indirectly detected by the above test using monoclonal antibodies against the mentioned subclasses. Curves obtained with aggregated IgG1 and/or IgG3 showed good sensitivity and specificity of the test. Complexes containing both IgG1 and IgG3 were present in sera from the majority of patients; however, the relative amounts of these subclasses varied from patient to patient.