Interaction of thyroid-stimulating antibody with Graves' thyroid-stimulating hormone-binding antibody.

OBJECTIVE: Evidence of anti-thyroid-stimulating hormone (TSH) antibody in Graves' serum has been reported. We found that extremely high Graves' anti-TSH antibodies neutralized other Graves' thyroid-stimulating antibody (TSAb) activity. METHOD: TSAb-IgG was affinity-purified by Sepharose-bound Graves' anti-TSH antibody (extremely high). RESULT: The thyroid-stimulating activity in affinity-purified TSAb-IgG increased about 4-5 times compared to that before purification. TSH-binding inhibitory immunoglobulin (TBII) activity in affinity-purified TSAb-IgG also increased using TSH receptor-coated tube assay. A similar increase of thyroid-stimulating activity accompanied with TBII activity was also observed in affinity-purified TSAb-IgG-F(ab')(2). CONCLUSION: This suggests the possibility that either TSAb may be an anti-idiotypic antibody against anti-TSH antibody or anti-TSH antibody may be an anti-idiotypic antibody against anti-TSH receptor antibody.

Immunological study of tissue polypeptide antigen (TPA)--demonstration of keratin-like sites and blood group antigen-like sites on TPA molecules.

We examined the immunological cross-reactivity between tissue polypeptide antigen (TPA) and keratin protein because of the reported sequence homology between these two proteins. TPA showed positive immuno-reactivity against both polyclonal and monoclonal antibodies for keratin. The binding of [125I]TPA with anti-keratin could be displaced dose-dependently by unlabeled keratin. However, no cross-reaction between keratin and anti-TPA was found. TPA also showed the positive immuno-reactivity with antibodies for blood group antigens (A, B and Lewis substances), but keratin did not. A standard solution of Lewis substance reacted with neither anti-TPA nor with anti-keratin. These data strongly suggest that TPA has an immunological similarity with both keratin protein and blood group antigens. When [125I]TPA and [125I]keratin were gel-filtered on a Sephadex G-200 column, the radioactivities of TPA and keratin were found mainly in the void volume fraction (MW greater than 200 000) and the MW of approximately 60 000, respectively. Chromatography on Sepharose 6B suggested that the MW of [125I]TPA was 320 000. When sera of cancer patients were gel-filtered on a Sephadex G-200 column, TPA activity was distributed mainly in the void volume fraction in all tested cases. This experiment suggests that TPA may be a glycoprotein (MW is 320 000) with both keratin-like and blood group antigen-like determinants.

Studies on circulating antibody against carcinoembryonic antigen (CEA) and CEA-like antigen in cancer patients.

Characteristics of auto-antibodies for carcinoembryonic antigen (CEA) detected in sera from 3 cancer patients (2 colorectal and 1 breast cancer) were examined. The antibodies belonged to polyclonal immunoglobulin G (IgG). The binding of auto-antibodies with the labeled CEA was inhibited by not only the unlabeled CEA but also NCA-2 (feces and meconium). However, no binding with NCA was observed. Among these auto-antibodies the antibody directed against blood group Lewis determinants which are known to be present in many purified CEA preparations was not found. Previously we had suggested that CEA, NCA-2 and NCA may contain immune determinant in common with alpha 1-acid glycoprotein (AG). These auto-antibodies showed significantly enhanced reactivity for the labeled CEA preparation after purification by anti-AG affinity chromatography in spite of no immunological reaction with AG. These results suggest that auto-antibodies are raised against the common antigenic determinants of both CEA and NCA-2 which do not exist in NCA. These antibodies might be directed to common amino acid sequence shared by CEA and NCA-2, though not excluding the carbohydrate moiety. We surveyed about 500,000 cancer patients but could find only 3 patients who showed a difference in the values of CEA by the indirect and direct method. Thus, the existence of this type auto-antibody to CEA in cancer patients is a rare phenomenon.

Immunochemical identification of an alpha 1-acid glycoprotein-antigenic determinant on carcinoembryonic antigen (CEA) and non-specific cross-reacting antigen (NCA).

An immunochemical characterization of carcinoembryonic antigen (CEA) and NCA (non-specific cross-reacting antigen) was performed. Positive reactions of CEA and NCA (Mr 60 000) with some antibodies to alpha 1-acid glycoprotein (AG) were observed. Thus, both antigens may contain immune determinants in common with alpha 1-acid glycoprotein. CEA showed positive reactivity with anti-NCA. NCA showed positive reactivity with either polyclonal or monoclonal antibodies to CEA, but negative reactivity with auto-antibodies to CEA. 125I-Tetracosapeptide (synthetic peptide-24 corresponding to the amino terminal sequence of CEA) failed to react with any antisera against CEA, NCA and AG. 125I-AG also showed no immuno-reaction with any antibody against CEA, NCA and tetracosapeptide. These results suggest that some monoclonal antibodies to CEA are directed against a common antigenic determinant of both CEA and NCA in addition to AG and tetracosapeptide, and that the auto-antibody to CEA is directed against a unique immune determinant which is not common to NCA. Thus, CEA appears to contain a unique determinant not found in NCA. Similarities in the composition of both amino acids and carbohydrates of CEA and NCA suggest that CEA is 'big-big' AG and NCA is 'big' AG.

Purification of carcinoembryonic antigen by affinity chromatography with anti-alpha 1-acid glycoprotein.

Purification of radiolabeled carcinoembryonic antigen (CEA) preparations by affinity chromatography with anti-AG bound to Sepharose was attempted, since an immunological similarity between AG (alpha 1-acid glycoprotein) and a portion of CEA had been noted. When 125I-CEA was purified in this manner, the fraction which did not bind to the column showed decreased reactivity with either anti-AG or anti-CEA. The retained fraction showed enhanced reactivity with both anti-AG and anti-CEA. The yield of purified CEA increased when the CEA preparation was allowed to react with the anti-AG column overnight. Purification of CEA from tumor tissue was performed by affinity chromatography. A perchloric acid (PCA) extract from cancer tissue was mixed with antiserum against CEA to give an immune complex, and a CEA-reactive fraction obtained by PCA extraction. The CEA-reactive fraction was eluted from a Sephadex G-200 column, and final purification was by anti-AG chromatography. When purified CEA was applied to a Sephadex G-200 column with carrier protein after labeling with 125I, the eluted radioactivity was found only in the 180,000 dalton fraction. Almost all the radioactivity was precipitated from the labeled protein by either anti-AG or anti-CEA. Purification of CEA is possible by affinity chromatography with anti-AG bound to Sepharose.