Studies on Organ Specificity

Abstract

Summary Antisera produced in rabbits by injection of crude extracts of thyroid glands gave crossreactions with thyroid extracts of various species in an irregular and unpredictable manner, thus exhibiting a pattern similar to that observed by Hektoen, Fox, and Schulhof (1) with isolated thyroglobulins. Basically, identical results were obtained by complement-fixation and precipitation techniques. Antisera produced in dogs by the injection of the same crude thyroid extracts also contained thyroid-specific antibodies. Cross-reactions with thyroid extracts of other species were considerably less prominent than in the case of rabbit antisera. There is a considerable variation in the extent of cross-reaction, depending upon the individual animal used for immunization. This observation makes general statements about the degree of cross-reaction most difficult. Absorption with human serum of a human thyroid antiserum containing antibodies against human serum as well as thyroid extracts of different species resulted in the elimination of the species-specific antibody without influencing the thyroid-specific antibodies. Absorption of the same antiserum with human thyroid extract (the homologous antigen) resulted in removal of the entire antibody content of the serum. Absorption with hog thyroid extract eliminated the cross-reaction with both hog thyroid and beef thyroid extract but did not reduce the strong reaction with the homologous human thyroid extract. These findings were substantiated by both complement-fixation and precipitation tests. The extent of cross-reactions of thyroid antisera with thyroid extracts of different species was estimated by diluting in the same experiment both antigen and antiserum. Cross-reactions with the thyroid extracts of different species were considerably weaker than the reactions with homologous antigen. There is also an important time element in the evaluation of serological reactions of this type. In complement-fixation tests, cross-reactions obtained with the thyroid of heterologous species disappeared rapidly after further incubation at 37°C, whereas the reaction with the homologous antigen did not decrease significantly. In precipitation tests, the homologous reactions appeared first, while the crossreactions manifested themselves after further standing. The cross-reactions of thyroid antisera with thyroid extracts of other species are thyroid-specific. No reactions were detected with other organs of the heterologous species.