Ki-1 (CD30) antigen is released by Ki-1-positive tumor cells in vitro and in vivo. I. Partial characterization of soluble Ki-1 antigen and detection of the antigen in cell culture supernatants and in serum by an enzyme-linked immunosorbent assay.
An enzyme-linked immunosorbent assay (ELISA) has been developed that allows the quantitative determination of the Ki-1 (CD30) antigen in soluble form. Similar levels of sensitivity of this new Ki-1 ELISA and the ELISA previously described for measuring the soluble 55-kDa chain of the interleukin 2 receptor were seen. As assessed with this ELISA, the investigated Ki-1+ permanent cell lines released the Ki-1 antigen into the culture supernatant. In culture supernatants of concanavalin A-activated human peripheral blood lymphocytes, however, this antigen could not be detected. The released Ki-1 antigen has an apparent molecular weight (Mr) of 85,000, whereas the cell-associated Ki-1 antigen has an Mr of 105,000. We investigated sera from 30 normal donors, 15 patients with systemic infections, and 63 patients suffering from lymphomas for soluble Ki-1 antigen. In all sera from normal donors and patients with systemic infectious diseases, soluble Ki-1 antigen was below the detection limit (i.e., less than 70 pg). In contrast, high amounts of the soluble Ki-1 antigen were found in sera from 18 malignant lymphomas containing Ki-1+ tumor cells. This finding demonstrates that the release of the Ki-1 antigen takes place not only in vitro, but in vivo as well. Moreover, these results imply that the Ki-1 antigen may be used as a serum tumor marker.
Josimovic-Alasevic
O
O
Institute of Immunology, Klinikum Steglitz, Free University of Berlin.
Dürkop
H
H
Schwarting
R
R
Backé
E
E
Stein
H
H
Diamantstein
T
T
D000328:Adult; D000911:Antibodies, Monoclonal; D000943:Antigens, Differentiation / Q000032:analysis*; D000951:Antigens, Neoplasm / Q000032:analysis*; D002474:Cell-Free System; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D017730:Ki-1 Antigen; D007700:Kinetics; D008223:Lymphoma / Q000276:immunology*; D008970:Molecular Weight; D015375:Receptors, Interleukin-2 / Q000032:analysis; D013347:Subcellular Fractions; D014407:Tumor Cells, Cultured
D000911:Antibodies, Monoclonal; D000943:Antigens, Differentiation; D000951:Antigens, Neoplasm; D017730:Ki-1 Antigen; D015375:Receptors, Interleukin-2