Detection of antibodies bound to tumor cell surface antigens with radioiodinated Staphylococcus aureus protein A (SPA).

Autor: Nayak, S., Knotts, F., Drogemuller, C., Pilch, Y.
Zdroj: Cancer Immunology, Immunotherapy; Feb1979, Vol. 5 Issue 4, p243-252, 10p
Abstrakt: Staphylococcal protein A (SPA) is known to bind to the Fc portion of certain subclasses of IgG. On the basis of this property, radioiodinated SPA (I-SPA) was used to detect antibodies reacting with surface antigens of tumor cells. Target cells derived from an osteosarcoma growing in C3H/fHeJ mice and antiserum to this tumor prepared in female Hartley guineapigs were used to establish optimum conditions for the assay. Similar optimum conditions were also determined for human melanoma target cells. Target cells were plated at a concentration of either 3×10 cells per well or 1×10 cells per well in Microtest II plates, and allowed to form semiconfluent monolayers for 24-48 h respectively. Target cells thus prepared were treated with antiserum and then with I-SPA. A minimum of 30 min incubation time was found to be optimal for the antigen-antibody reaction. The quantity of I-SPA bound to antisera-treated target cells was found to depend on the time of incubation with I-SPA and on the concentration of SPA used. Longer incubation times and increasing concentrations of SPA resulted in greater amounts of I-SPA being bound to antiserum treated target cells. This assay was employed for the detection of antibodies in the sera of two melanoma patients and two colon carcinoma patients. The results of absorption analysis suggest that the antibody activity in the sera of the melanoma patients may be of four different specificities: (a) autoantibodies, (b) alloantibodies, (c) antibodies reacting with common, cross-reacting melanoma-associated antigens, and (d) antibodies reacting with unique antigens specific for autologous melanoma cells. [ABSTRACT FROM AUTHOR]
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