'In vitro' study of a reaction between the complement system and cellular DNA.

A direct reaction between the complement system and DNA in nuclei was demonstrated in vitro by an indirect immunofluorescence technique using cryostat-cut sections of rat liver as a substrate. This reaction occurred at physiological conditions of pH and molarity and was abolished by pre-treatment of the tissue sections by DNase. It begins by the fixation of C1q and involves the fixation and probably the activation of apparently all the components of the classical pathway of the complement system. The pattern of fluorescence given by this reaction was similar to the pattern given by anti-DNA antibodies present in sera from systemic lupus erythematosus (SLE) patients.