In vitro production of thyroid-binding antibodies by peripheral blood lymphocytes from patients with Graves' disease: nonspecific responses associated with culture supernatant proteins.

Peripheral blood lymphocytes from patients with Graves' disease were cultured for 7 days with mitogens (phytohemagglutinin, Concanavalin A, protein A), or specific antigen (thyroid membranes), in an attempt to produce thyroid-binding antibodies (TBAb) in vitro. TBAb was measured in culture supernatants using a sensitive radioreceptor assay. Mean TBAb indices of mitogen or antigen-stimulated cultures did not differ significantly from those of unstimulated cultures for either patients or normal subjects. Although TBAb indices of less than 0.70, which are generally considered positive for serum TBAb, were demonstrated in a small proportion of individual tests of supernatants from patients with Graves' disease, low indices were also found in tests from normal subjects. One cause of such nonspecific responses was found to be culture infection. The factor associated with positive responses in infected cultures was unlikely to be an immunoglobulin since TBAb-like activity was not detected in globulins isolated by DEAE + -Sephadex chromatography, which isolates only IgG and IgA, and the activity was not neutralized by anti-IgG serum. The possible ways of improving the culture system for in vitro TBAb production and the significance of nonspecific responses in the radioreceptor assay are discussed.