Detection of nucleosome-IgG immune complexes in ascites from mice transplanted with anti-DNA antibody-secreting hybridomas and in plasmas from MRL-lpr/lpr mice

Autoantibodies directed against chromatin components characterize lupus diseases. Immune complexes made of these autoantibodies bound to nucleosomes released from dead cells could play some pathogenic role. The aims of this study were to investigate if nucleosome-IgG complexes could contaminate IgG anti-DNA MoAb preparations, and if such complexes circulate in lupus diseases. A new method was set up using preformed nucleosome-IgG complexes. Complexes were adsorbed onto microplate through Fc binding and nucleosomal DNA was detected by internal incorporation of labelled nucleotide. Using this method, high amounts of complexes were found in ascites from mice transplanted with anti-DNA antibody-secreting hybridomas. In some ascites, nucleosome was found to be strongly associated with the MoAb, confirming that nucleosome-IgG complexes could contaminate monoclonal autoantibody preparations. In MRL-lpi/lpr mice, nucleosome-IgG complexes were detected at 16-24 weeks of age at a time when kidney lesions are rapidly worsening, raising the question of their pathogenic significance.