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.