In Vivo Behavior of Homologous and Heterologous Thyroglobulin and Induction of Immunologic Unresponsiveness to Heterologous Thyroglobulin

Summary Homologous and heterologous thyroglobulins were observed to have an in vivo behavior, following injection, very similar to that of homologous and heterologous serum proteins. Following injection, thyroglobulin equilibrated between the intra- and extravascular fluid spaces, and persisted in both the blood and lymph with elimination at an exponential rate. A consistent immune response was made to the injected heterologous thyroglobulin but not to the injected homologous thyroglobulin. As with serum proteins, the half-life of heterologous thyroglobulin was usually shorter than the homologous thyroglobulin and varied with the host animal. An acquired immunologic unresponsiveness was induced in rabbits by periodic injections of a heterologous bovine thyroglobulin starting on the day of birth. Thyroglobulin was found to be an excellent antigen for the study of various immunological mechanisms. In addition to the properties listed above, in small doses heterologous thyroglobulins induce a much greater antibody response than comparable heterologous serum proteins.