Polyreactivity is a Property of Natural and Disease‐Associated Human Autoantibodies

Polyreactivity was earlier recognized as a feature of naturally expressed autoantibodies in serum. In the present study, we have compared the reactivity on a panel of self antigens of affinity‐purified anti‐DNA and anti‐thyroglobulin (TG) IgG autoantibodies from the serum of patients with systemic lupus erythematosus (SLE) and autoimmune thyroiditis with their affinity‐purified counterparts isolated from the serum of healthy individuals. Anti‐DNA autoantibodies exhibited a similar degree of polyreactivity whether originating from patients or from healthy adults. Natural anti‐TG autoantibodies were also found to be polyreactive. Anti‐TG autoantibodies from patients with Hashimoto's thyroiditis showed little or no polyreactivity. Natural anti‐TG autoantibodies were equally polyreactive whether or not they belonged to a fraction of normal IgG that is connected through V regions with other IgG molecules from the same source. These results indicate that polyreactivity of autoantibodies is a feature that does not allow one to distinguish between natural and disease‐associated autoantibodies as well as between V‐region‐connected and unconnected autoantibodies.