Anti-DNA activity of IgG F(ab')₂ from normal human serum

The components of normal human serum (NHS) which bound DNA in a standard assay for anti-DNA antibody were characterized. IgG was the major detectable protein isolated from NHS by affinity chromatography on DNA-cellulose. A second adsorption of the whole serum IgG with DNA-cellulose did not remove additional γ-globulin indicating that only a very small fraction of the IgG was capable of binding DNA. This binding activity was largely restricted to denatured DNA. IgG (Fab')₂ bound DNA as well as the intact molecules demonstrating the antibody-like nature of the IgG binding. These results suggest that IgG antibody to denatured DNA is a normal component of human serum.