Polyclonal Human Antibodies to IgG (Rheumatoid Factors) Which Cross‐React with Cell Nuclei

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Abstract
Antibodies to human IgG [immunoglobulin G] (rheumatoid factors [RF]) from serum Han resembled the intermediate complexes of sera from some patients with rheumatoid arthritis. These RF were isolated from heat-inactivated serum by affinity chromatography on agarose-coupled human IgG. Indirect immunofluorescence revealed that the isolated RF cross-reacted with cell nuclei from many species. Virtually all the antinuclear factor (ANF) activity of this serum was extracted by IgG-agarose. Alternative explanations of this phenomenon, such as nonspecific binding of a separate population of ANF, binding of ANF to the immunosorbent via an IgG RF-IgG ANF immune complex, or presence of nuclear antigens on the immunosorbent, were ruled out. The cross-reacting antibodies possessed .kappa. and .lambda. light [L] chains and predominantly .gamma. and some .mu. heavy [H] chains, indicating that they were of polyclonal origin. The antinuclear activity was present in the F(ab'')2 fragments. The interpretation of this cross-reaction is discussed.