Detection of DNA-bound immunoglobulins in patients with lupus nephritis, using monoclonal anti-DNA antibody

Physical and biological studies on DNA/anti-DNA immune complex formed in vitro

In vitro preparation of DNA/anti-DNA immune complex using monoclonal antibody and low molecular weight homogeneous DNA was described and the characteristics of the immune complex were identified. The immune complex was formed by the monoclonal antibody with DNA effectively at high ratios of antibody/DNA. The activation and binding ability of the immune complex to the complement was considerably high, whereas the capacity to bind red blood cells via C3b complement component receptor was shown relatively low. The assay of sucrose density gradient ultracentrifugation indicated that the sedimentation coefficient of the immune complex was between 10S and 23S. Studies of organ distribution and uptake of IC demonstrated a particular affinity to the kidney tissue. The significance of these results with respect to the latent pathogenicity of the immune complex was discussed.

Ultrastructural localization of DNA in immune deposits of human lupus nephritis

DNA molecules were revealed in the glomerular wall of lupus nephritis patients by applying two specific colloidal gold cytochemical approaches at the electron microscope level: immunocytochemistry using a monoclonal anti-DNA antibody in conjunction with protein A-gold and enzyme-gold cytochemistry using DNAse-gold complexes. Application of both techniques has demonstrated that DNA molecules are preferentially located over the electron-dense deposits found in the glomerular basement membrane and mesangial matrix of SLE patients, as well as over the nuclei. Their distribution within the glomerular wall was correlated with electron-dense immune deposits revealed by anti-light chain antibodies. In normal control kidney, DNA labeling was restricted to the cell nuclei. Several control experiments have demonstrated the high specificity of the results. These data thus suggest a possible role for DNA as an antigenic component in the formation of immune complexes.