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.
Ochi
Y
Y
Ura
Y
Y
Hamazu
M
M
Ishida
M
M
Kajita
Y
Y
Nakajima
Y
Y
D000918:Antibody Specificity; D001789:Blood Group Antigens / Q000276:immunology*; D002850:Chromatography, Gel; D000939:Epitopes / Q000032:analysis*; D006801:Humans; D007120:Immunochemistry; D007633:Keratins / Q000276:immunology*; D009369:Neoplasms / Q000276:immunology; D010455:Peptides / Q000276:immunology*; D011863:Radioimmunoassay; D019396:Tissue Polypeptide Antigen
D001789:Blood Group Antigens; D000939:Epitopes; D010455:Peptides; D019396:Tissue Polypeptide Antigen; D007633:Keratins