Comparison of multiple assays for detecting human antibodies directed against surface antigens on normal and malignant human tissue culture cells

Tumor-associated blood group antigen expressions and immunoglobulins associated with tumors

As outlined in Figures 1 and 2, the biosynthetic pathways for the expression of the A, B and H, and the Lewis determinant carbohydrate sequence structures, as well as sialylated structures, involves both type 1 and type 2 precursor chains (which may be present as glycolipids and N- or O-linked glycoproteins), and many glycosyltransferases. For tumor cells, there appears to be increased expressions of fucosyl- and sialyltransferases yielding such structures as the Le(x), sialyl-Le(a), and many other similar determinants, which are not found on the normal cell progenitor of the tumor. The types of structures expressed on tumor cells is dependent on the particular fucosyl-, sialyl- and other glycosyltransferase genes activated in the transformation and tumor progression events, the availability of the substrates for the glycosyltransferases (both the precursor sequences and the nucleotide-sugar substrates) which is partly dependent on metabolites available to the tumor mass, and on the genotype of the individual regarding particular glycosyltransferases. Both the loss of A, B and/or H blood group antigen expressions of tumor cells and the relative expressions of the Lewis and sialylated-oligosaccharide determinants may be a consequence of the competing biosynthetic pathways and the glycosyltransferases for common substrate sequences, as well as due to the loss of particular glycosyltransferases concomitant with transformation. All of these factors probably account for the variable expressions of the complex of carbohydrate sequence determinants when comparing tumor sections of different individuals as well as the heterogeneity of expression of particular determinants within a single tumor tissue section. As described above, the A, B and/or H determinants, and the precursor sequences, are also expressed to differing extents on epithelial cells depending on the tissue type and cellular location in the tissue. Thus, the differentiation state of the particular epithelial cell also determines the quantity and types of carbohydrate sequences expressed. However, because of the complex nature of the competing biosynthetic pathways for the carbohydrate sequences of glycolipids and glycoproteins, and the relative activations of fucosyl- and sialyltransferases of tumor cells, it would seem that simple deductions as to the state of differentiation of particular tumors with A, B, H and precursor sequence expressions is not warranted.(ABSTRACT TRUNCATED AT 400 WORDS)

Demonstration of specific serologic reactivity in human osteosarcoma

Cultured cell lines of osteosarcoma and normal skin fibroblasts were derived from tissues of five patients with localized osteosarcoma. Testing of pretreatment patient sera in an indirect immunofluorescence assay against both autologous normal fibroblasts and autologous osteosarcoma cells showed cytoplasmic staining. Quantitative absorption of patient sera with human fetal cells removed all reactivity against autologous fibroblasts, but fetal-absorbed sera showed cytoplasmic, membrane, and nuclear fluorescence when tested against autologous osteosarcoma. Testing the five patient sera against all five cell lines showed staining of allogeneic fibroblasts and osteosarcoma by nonabsorbed sera. Following fetal absorption, all reactivity against fibroblasts was removed, with the retention of specific staining of all osteosarcoma cell lines by all five patient sera. Additional testing of sera from normal patients, patients with soft tissue sarcomas, and patients with melanoma showed staining of allogeneic cultured fibroblasts and tumor cells derived from a patient with osteosarcoma. All staining against fibroblasts and tumor cells was eliminated by fetal absorption of the allogeneic sera. Results suggested that fetal neoantigens are expressed in cultured normal and malignant cell lines and that such fetal antigens are recognized by natural antibodies. Absorption of antifetal reactivity allowed demonstration of specific serum reactivity against osteosarcoma cells.

"Membrane-associated" immunoglobulins in cyst and ascites fluids of ovarian cancer patients

A new column chromatography technique, utilizing peroxidase-labeled antihuman immunoglobulins, is described, which can measure the binding of specific antibodies to membrane fragments containing relevant antigens. Using this assay, the presence of bound immunoglobulin is demonstrated on membrane fragments isolated from ascites fluids, but not from tumor tissues. In this study, two populations of immunoglobulins were examined: 'free' immunoglobulins and immunoglobulins bound to ascites fluid-derived membrane fragments. Immunoglobulins eluted from membrane fragments of the ascites fluids were capable of binding to the tumor. These were specific for binding to tumor membrane preparations, in that there was two orders of magnitude greater binding of these immunoglobulins at a given concentration than 'free' immunoglobulins at the same concentration.

Human melanoma associated antigens: a solid-phase assay for detection of specific antibody

A solid-phase radioimmunometric binding assay is described utilizing 125I-labeled protein A for the detection of antibody to human melanoma associated antigens. The novel aspect of this assay is the use of chemically defined spent culture medium of melanoma cells at target antigens previously depleted of fibronectin by affinity chromatography. This makes it possible to screen for antibody in unabsorbed antiserum. Sensitivity, reproducibility and ease of performance of the assay are optimized by conjugating target antigens to a background of bovine serum albumin dried onto polyvinyl 96-well microtiter plates and cross-linked with glutaraldehyde. The use of an immobilized soluble antigen target derived from a large pool of spent culture medium facilitates direct interassay comparisons and permits extensive absorption analysis of antisera. The assay has considerable potential in screening for alloantibody and both poly- and monoclonal xeonoantibody to human melanoma associated antigens.

A comparison of two techniques for the detection of an antibody in human serum to Chang liver cell surface antigens

The antibody-dependent cell-mediated cytotoxicity technique (ADCC) and an isotopic antiglobulin technique have been compared for their abilities to detect human serum antibodies to Chang liver cell membrane antigens. The optimal conditions were established for the latter technique, which was found to be superior with respect to reproducibility and sensitivity. Also, unlike ADCC, the isotopic antiglobulin technique was unaffected by other factors, such as immune complexes present in pathological sera.

Protein-A antibody-binding TPAAB) technique for detection of tumor-associated membrane antigen (TAMA) of Lewis lung carcinoma

Xenoantisera were prepared in rabbits against intact paraformaldehyde-fixed Lewis lung carcinoma (LLCa) cells and membrane solubilized proteins extracted with Triton X-100 and 3M KCI. The antisera were analyzed for antibodies to tumor-associated membrane antigens (TAMA) by means of a solid-phase radioimmunoassay (RIA). THe immunoassay employed 125-labelled Staphylococcus aureus protein A (SPA) to detect specific antibody binding to glutaraldehyde-fixed Lewis lung tumor target cells. The protein-A antibody-binding (PAAB) method is rapid, sensitive and reproducible. The PAAB revealed a possible LLCa-TAMA as evidenced by the reactivity of xenoantisera raised to LL paraformaldehyde tumor cell vaccine (TCV) and LL tumor Triton X-100 (TTri) and 3M KCI (TKCI) extracts of membrane preparations. The reactivity of our antisera followed linear dose-response kinetics but the degree of reactivity decreased from anti-TCV to anti-TTri to anti-TKCI respectively. The LL-TAMA demonstrated specificity since our antisera did not significantly cross-react with normal C56BL/6 cellular antigens or other known murine tumor-associated surface antigens of virally and chemically-induced tumor systems.

Comparison of multiple rosetting assays for detecting antibody reactivity of different immunoglobulin classes against surface antigens of benign and malignant tissue culture cells

Four serological assays for detection of antibody reactivity against surface antigens of benign and malignant cells have been evaluated. In all four assays, antibody attached to the surface of a target cell is detected by a rosette of indicator red blood cells. Of the four assays (antibody mixed hemadsorption assay, immune adherence assay, anti-C3 mixed hemadsorption assay and protein A assay), the anti-C3 mixed hemadsorption assay showed highest sensitivity. By using purified IgM and IgG fractions we could demonstrate that, except for the protein A assay, all assays show reactivity both with IgG and IgM. Protein A assay detected only the IgG fraction, with high sensitivity. The optimization of the four assays is described and the importance of using multiple assays is emphasized.

A sensitive assay for the detection cytotoxic antibodies to mammalian cell surface antigens

A microcytotoxicity assay for the detection of complement-dependent serum toxicity against adherent cells has been modified to include post-labeling of the target cells with [3H]leucine or [3H]thymidine. The adaptation represents a significant improvement over the visual counting of residual cells. The technique is more objective and less tedious than the original procedure, while retaining the features of economy of cells and sera, reproducibility, and sensitivity. Examples are given which demonstrate the suitability of the modified assay for the analysis of human and mouse tumor antigens using autologous, allogeneic, and syngeneic sera.

Sensitive and convenient quantitation of antibody binding to cellular antigens using glutaraldehyde preserved cells

As a preliminary step in the identification and isolation of antibodies to human cancers, we have developed a sensitive and convenient assay for antibody binding to cellular antigens. The basis for the method is antibody binding to glutaraldehyde-fixed cells (AbGfC) and quantitation with radioiodinated staphylococcal protein A (SpA). Glutaraldehyde fixation of intact cells, which does not appear to effect the ability to form antigen-antibody complexes, provides a convenient and standard supply of target cells which may be stored at 4 degrees C and used in the assay over a period of several months. The amount of antibody specifically bound to the cells is quantitated by the addition of 125I-labeled SpA. The sensitivity of the method was compared with two complement-dependent cytotoxicity methods (trypan blue exclusion and 51Cr release assays) and tested with two antisera to human lung cancer and one antiserum to a membrane antigen of a murine lymphoma. These comparisons indicated much greater sensitivity when compared with the trypan blue exclusion assay and equivalent sensitivity with greater dose response characteristics when compared with the 51Cr release assay.