Non-precipitating antithyroglobulin studied by the Ouchterlony technique.

Non-precipitating antibody reacting with human thyroglobulin has been found in the serum of a patient with Hashimoto's disease. On Ouchterlony plates this antibody causes a clear line to develop in the slightly cloudy agar instead of the usual dense white precipitate: it is capable of blocking the action of certain precipitating Hashimoto sera, whereas other `enhancing' Hashimoto sera enable the non-precipitating serum to take part in precipitate formation. A consideration of this phenomenon suggests that the non-precipitating serum reacts at different sites on the same antigen molecule from the enhancing serum. This reaction provides a mechanism whereby two lines of precipitate may be formed in agar with a single pure antigen.